Document community extensions [skip ci] (#554)

README.rst

@@ -13,6 +13,7 @@ Gazelle build file generator
 .. _Avoiding conflicts with proto rules: https://github.com/bazelbuild/rules_go/blob/master/proto/core.rst#avoiding-conflicts
 .. _gazelle rule: #bazel-rule
 .. _Extending Gazelle: extend.rst
+.. _Supported languages: extend.rst#supported-languages
 .. _extended: `Extending Gazelle`_
 .. _gazelle_binary: extend.rst#gazelle_binary
 .. _import_prefix: https://docs.bazel.build/versions/master/be/protocol-buffer.html#proto_library.import_prefix
@@ -52,6 +53,7 @@ may change. Gazelle is not an official Google product.*
   * `http_archive`_ (deprecated)
 
 * `Extending Gazelle`_
+* `Supported languages`_
 * `Avoiding conflicts with proto rules`_
 
 Setup

extend.rst

@@ -12,6 +12,9 @@ Extending Gazelle
 .. _proto godoc: https://godoc.org/github.com/bazelbuild/bazel-gazelle/language/proto
 .. _proto.GetProtoConfig: https://godoc.org/github.com/bazelbuild/bazel-gazelle/language/proto#GetProtoConfig
 .. _proto.Package: https://godoc.org/github.com/bazelbuild/bazel-gazelle/language/proto#Package
+.. _rules_sass: https://github.com/bazelbuild/rules_sass
+.. _#75: https://github.com/bazelbuild/rules_sass/pull/75
+.. _bazel_rules_nodejs_contrib: https://github.com/ecosia/bazel_rules_nodejs_contrib#build-file-generation
 
 .. role:: cmd(code)
 .. role:: flag(code)
@@ -37,6 +40,18 @@ To extend Gazelle, you must do three things:
   ``bazel run //:gazelle``, your binary will be built and executed instead of
   the default binary.
 
+Supported languages
+-------------------
+
+Some extensions have been published by the community.
+
+* `rules_sass`_ has an extension for generating ``sass_library`` and
+  ``sass_binary`` rules (currently pending in PR `#75`_).
+* Ecosia's `bazel_rules_nodejs_contrib`_ has an extension for generating
+  ``js_library``, ``jest_node_test``, ``js_import``, and ``ts_library`` rules.
+
+If you have an extension you'd like linked here, please open a PR!
+
 Example
 -------