DOCS: Mention the mdformat GitHub topic (#450)

* Mention the mdformat GitHub topic in the docs

* Format docs

Author: hukkin

docs/contributors/contributing.md

@@ -60,11 +60,11 @@ setuptools.setup(
 )
 ```
 
-If using Poetry for packaging, the entry point configuration in `pyproject.toml` would need to be like:
+If using a PEP 621 compliant build backend (e.g. Flit) for packaging, the entry point configuration in `pyproject.toml` would need to be like:
 
 ```toml
 # other config here...
-[tool.poetry.plugins."mdformat.codeformatter"]
+[project.entry-points."mdformat.codeformatter"]
 "python" = "my_package.some_module:format_python"
 ```
 
@@ -112,10 +112,17 @@ setuptools.setup(
 If using Poetry or Flit for packaging, the entry point configuration in `pyproject.toml` would need to be like:
 
 ```toml
-# other config here...
+# Poetry specific:
 [tool.poetry.plugins."mdformat.parser_extension"]
 "myextension" = "my_package:ext_module_or_class"
-# or
-[tool.flit.plugins."mdformat.parser_extension"]
+```
+
+```toml
+# or PEP 621 compliant (works with Flit):
+[project.entry-points."mdformat.parser_extension"]
 "myextension" = "my_package:ext_module_or_class"
 ```
+
+## Making your plugin discoverable
+
+In case you host your plugin on GitHub, make sure to add it under the "mdformat" topic so it shows up on https://github.com/topics/mdformat.

docs/users/plugins.md

@@ -23,7 +23,7 @@ formatted = mdformat.text(unformatted, codeformatters={"python"})
 assert formatted == '```python\n"""black converts quotes"""\n```\n'
 ````
 
-### Existing plugins
+### Existing plugins (see https://github.com/topics/mdformat for more!)
 
 <table>
   <tr>
@@ -90,7 +90,7 @@ unformatted = "content...\n"
 formatted = mdformat.text(unformatted, extensions={"tables"})
 ```
 
-### Existing plugins
+### Existing plugins (see https://github.com/topics/mdformat for more!)
 
 <table>
   <tr>