Documentation: replace m2r2 with myst-parser

sphinx recommends myst-parser for markdown conversion:
https://www.sphinx-doc.org/en/master/usage/markdown.html

m2r2 is not supported for Python versions >= 3.12 so
we can't build Documentation for example on latest Arch Linux

by the way myst-parser detected a bad link to SECURITY.md that is now fixed

Documentation/Pipfile

@@ -7,7 +7,7 @@ verify_ssl = true
 
 [packages]
 docutils = "==0.18.1"
-m2r2 = "==0.3.2"
+myst-parser = "*"
 sphinx_rtd_theme = "*"
 Sphinx = "~=6.0"
 sphinx-tabs = "*"

Documentation/conf.py

@@ -53,7 +53,7 @@ version = release = "latest"
 # ones.
 extensions = [
     "sphinx_rtd_theme",
-    "m2r2",
+    "myst_parser",
     "sphinx.ext.autosectionlabel",
     "sphinx.ext.todo",
     "sphinx_tabs.tabs",

Documentation/introduction/inviolables.rst

@@ -1 +1,2 @@
-.. mdinclude:: ../../INVIOLABLES.md
+.. include:: ../../INVIOLABLES.md
+   :parser: myst_parser.sphinx_

Documentation/introduction/resources.rst

@@ -23,4 +23,5 @@ Here's a list of Apache NuttX resources that you might find helpful:
 Legacy README
 =============
 
-.. mdinclude:: ../legacy_README.md
+.. include:: ../legacy_README.md
+   :parser: myst_parser.sphinx_

Documentation/legacy_README.md

@@ -96,7 +96,8 @@ Get help using NuttX or contribute to the project on our mailing lists:
 
 ## Reporting Security Issues
 
-Found a vulnerability? See our security policy [here](.github/SECURITY.md).
+Found a vulnerability? See our security policy
+[here](https://github.com/apache/nuttx/blob/master/.github/SECURITY.md).
 
 ## Issue Tracker