doc: add krita plugins section

doc/packages/index.md

@@ -14,6 +14,7 @@ fish.section.md
 fuse.section.md
 ibus.section.md
 kakoune.section.md
+krita.section.md
 linux.section.md
 locales.section.md
 etc-files.section.md

doc/packages/krita.section.md

@@ -0,0 +1,37 @@
+# Krita {#sec-krita}
+
+## Python plugins {#krita-python-plugins}
+
+"pykrita" plugins should be installed following
+[Krita's manual](https://docs.krita.org/en/user_manual/python_scripting/install_custom_python_plugin.html).
+This generally involves extracting the extension to `~/.local/share/krita/pykrita/`.
+
+## Binary plugins {#krita-binary-plugins}
+
+Binary plugins are Dynamically Linked Libraries to be loaded by Krita.
+
+_Note: You most likely won't need to deal with binary plugins,
+all known plugins are bundled and enabled by default._
+
+### Installing binary plugins {#krita-install-binary-plugins}
+
+You can choose what plugins are added to Krita by overriding the
+`binaryPlugins` attribute.
+
+If you want to add plugins instead of replacing, you can read the
+list of previous plugins via `pkgs.krita.binaryPlugins`:
+
+```nix
+(pkgs.krita.override (old: {
+    binaryPlugins = old.binaryPlugins ++ [ your-plugin ];
+}))
+```
+
+### Example structure of a binary plugin {#krita-binary-plugin-structure}
+
+```
+/nix/store/00000000000000000000000000000000-krita-plugin-example-1.2.3
+└── lib
+   └── kritaplugins
+      └── krita_example.so
+```