Add list of third-party plugins (#8910)

Co-authored-by: Hugo van Kemenade <[email protected]>

Author: radarhere

docs/handbook/appendices.rst

@@ -8,4 +8,5 @@ Appendices
 
   image-file-formats
   text-anchors
+  third-party-plugins
   writing-your-own-image-plugin

docs/handbook/third-party-plugins.rst

@@ -0,0 +1,18 @@
+Third-party plugins
+===================
+
+Pillow uses a plugin model which allows users to add their own
+decoders and encoders to the library, without any changes to the library
+itself.
+
+Here is a list of PyPI projects that offer additional plugins:
+
+* :pypi:`DjvuRleImagePlugin`: Plugin for the DjVu RLE image format as defined in the DjVuLibre docs.
+* :pypi:`heif-image-plugin`: Simple HEIF/HEIC images plugin, based on the pyheif library.
+* :pypi:`jxlpy`: Introduces reading and writing support for JPEG XL.
+* :pypi:`pillow-heif`: Python bindings to libheif for working with HEIF images.
+* :pypi:`pillow-jpls`: Plugin for the JPEG-LS codec, based on the Charls JPEG-LS implemetation. Python bindings implemented using pybind11.
+* :pypi:`pillow-jxl-plugin`: Plugin for JPEG-XL, using Rust for bindings.
+* :pypi:`pillow-mbm`: Adds support for KSP's proprietary MBM texture format.
+* :pypi:`pillow-svg`: Implements basic SVG read support. Supports basic paths, shapes, and text.
+* :pypi:`raw-pillow-opener`: Simple camera raw opener, based on the rawpy library.