fonts: added fonts and guide for linux

wiki/font.md

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+# Font
+
+A fonts is the particular size, weight and style of a typeface.
+Operating systems based on [Linux](/wiki/linux/linux.md) handle fonts by the
+[fontconfig package](/wiki/linux/font_configuration.md).
+
+## Typefaces
+
+Typefaces or font families can be roughly divided into the following styles:
+
+- Serif typefaces use serifs - the small feature at the end of the strokes
+  within letters.
+- Sans-serif typefaces do not use serifs.
+- Monospace typefaces are typefaces with all glyphs having the same width.
+
+Depending on the usage and definition japanese, chinese and korean fonts can be
+seen as a separate style.

wiki/linux/font_configuration.md

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+# Font Configuration
+
+This entry addresses the handling of [fonts](/wiki/font.md) for
+[Linux-based](/wiki/linux/linux.md) operating systems.
+
+## Setup
+
+Fontconfig is the standard library used to customize and configure.
+On most [Linux](/wiki/linux/linux.md) distributions fontconfig can be setup by
+installing the package `fontconfig`.
+
+### Configuration
+
+The configuration file is usually stored in the file
+`~/.config/fontconfig/fonts.conf`.
+A configuration typically looks like the following lines.
+
+```xml
+<?xml version='1.0'?>
+<!DOCTYPE fontconfig SYSTEM 'fonts.dtd'>
+<fontconfig>
+	<alias>
+		<family>serif</family>
+		<prefer>
+			<family>Linux Libertine</family>
+			<family>Joy Pixels</family>
+		</prefer>
+	</alias>
+	<alias>
+		<family>sans-serif</family>
+		<prefer>
+			<family>Linux Biolinum</family>
+			<family>Joy Pixels</family>
+		</prefer>
+	</alias>
+	<alias>
+		<family>monospace</family>
+		<prefer>
+            <family>JetBrainsMono Nerd Font Mono</family>
+			<family>Joy Pixels</family>
+		</prefer>
+	</alias>
+</fontconfig>
+```
+
+This configuration requires some fonts that are not necessarily present in any
+Linux installation so they may have to be installed.
+Follow the section on [adding new fonts](#adding-new-font) and
+[recommended fonts](#recommended-fonts) as needed.
+
+## Usage
+
+This section addresses important commands and packages for the configuration of
+fonts.
+
+### List or Find Font Family
+
+A list of all fonts can be displayed using the command `fc-match -a`.
+If the name of the font is not clear the command
+`fc-match -a | grep <search term>` can be used to get an overview of the fonts
+available.
+For matching the command `fc-match -s <search term>` is be used.
+This will display a list of font families that match best with the given search
+term.
+
+### Adding New Font
+
+A new font can be added by placing its name inside `<family>`/`</family>`-tags.
+Make sure to place it inside the correct [font family](/wiki/font.md#typefaces).
+If you want to add a font into the configuration make sure its name
+[matches](#list-or-find-font-family) correctly.
+
+### Recommended Fonts
+
+In this section various fonts are listed for the different typefaces.
+Make sure to follow [the adding new fonts section](#adding-new-font) after
+installing new fonts.
+
+#### Monospace
+
+For monospace the font `JetBrainsMono Nerd Font Mono` that is also used
+IntelliJ and other JetBrains software is recommended.
+As an additional feature it can be used packaged as a
+[Nerd Font](https://www.nerdfonts.com/).
+For some distributions it is available in the `ttf-jetbrains-mono-nerd` package.
+alternatively it can be downloaded from the
+[Nerd Fonts download page](https://www.nerdfonts.com/font-downloads).
+
+#### CJK
+
+CJK fonts can be installed together by using Google Noto CJK fonts.
+They are typically inside a package named `noto-fonts-cjk` but can also be
+retrieved from their [website](https://fonts.google.com/noto).
+
+An alternative to this are the Adobe fonts.
+They are typically installed separately.
+The repository is split into
+[source han sans](https://github.com/adobe-fonts/source-han-sans),
+[source han serif](https://github.com/adobe-fonts/source-han-serif) and
+[source han mono](https://github.com/adobe-fonts/source-han-mono) .
+On some [package managers](/wiki/linux/package_manager.md) the fonts are further
+split depending on [typeface](/wiki/font.md#typefaces) and language.
+The following list shows the name of the
+[Arch Linux packages](/wiki/linux/arch-linux/arch-linux.md).
+The names on other distributions can vary slightly.
+
+- `adobe-source-han-sans-jp-fonts` is for japanese sans style fonts.
+- `adobe-source-han-serif-jp-fonts` is for japanese sans style fonts.
+- `adobe-source-han-mono-jp-fonts` is for japanese mono style fonts.
+- `adobe-source-han-sans-kr-fonts` is for korean sans font.
+- `adobe-source-han-serif-kr-fonts` is for korean serif font.
+- `adobe-source-han-mono-kr-fonts` is for korean mono font.
+
+#### Emojis
+
+Emojis are typically unicode characters that need special packages to be
+displayed properly.
+
+[JoyPixels](https://joypixels.com) feature many emoji icons.
+The fonts can be obtained from their [website](https://joypixels.com/download)
+or for most distributions from the `ttf-joypixels` package.