readme: change format from markdown to rst

Fixes issue `twine check` had with markdown code blocks that blocked
uploading wheels to pypi. Also, rst files fit better with the python doc
environment anyway and more may be added in the future for API
documentation purposes.

Author: radhermit

README.md

@@ -0,0 +1,60 @@
+|CI| |coverage| |pypi|
+
+===============
+pkgcraft-python
+===============
+
+Python bindings for pkgcraft_.
+
+Install
+=======
+
+Install pre-built package from pypi::
+
+    pip install pkgcraft
+
+Install from git (assumes pkgcraft-c has been installed from git and cython is
+available)::
+
+    pip install https://github.com/pkgcraft/pkgcraft-python/archive/master.tar.gz
+
+Install from a tarball (assumes required release of pkgcraft-c is installed)::
+
+    python setup.py install
+
+Development
+===========
+
+Requirements: >=python-3.9, tox_, valgrind_, and everything required to build
+pkgcraft-c_
+
+Use the following commands to set up a dev environment:
+
+.. code-block:: bash
+
+    # clone the pkgcraft workspace and pull the latest project updates
+    git clone --recurse-submodules https://github.com/pkgcraft/pkgcraft-workspace.git
+    cd pkgcraft-workspace
+    git submodule update --recursive --remote
+
+    # build pkgcraft-c library and set shell variables (e.g. $PKG_CONFIG_PATH)
+    source ./build pkgcraft-c
+
+    cd pkgcraft-python
+    # build and test
+    tox -e python
+
+For development purposes, testing is performed under tox using varying targets
+for different functions. Use **tox list** to see all the target descriptions.
+
+.. _tox: https://pypi.org/project/tox/
+.. _valgrind: https://valgrind.org/
+.. _pkgcraft: https://github.com/pkgcraft/pkgcraft
+.. _pkgcraft-c: https://github.com/pkgcraft/pkgcraft-c
+
+.. |CI| image:: https://github.com/pkgcraft/pkgcraft-python/workflows/CI/badge.svg
+   :target: https://github.com/pkgcraft/pkgcraft-python/actions/workflows/ci.yml
+.. |coverage| image:: https://codecov.io/gh/pkgcraft/pkgcraft-python/branch/main/graph/badge.svg
+   :target: https://codecov.io/gh/pkgcraft/pkgcraft-python
+.. |pypi| image:: https://img.shields.io/pypi/v/pkgcraft.svg
+   :target: https://pypi.python.org/pypi/pkgcraft

README.rst

@@ -21,7 +21,7 @@ dynamic = ["version", "readme"]
 homepage = "https://github.com/pkgcraft/pkgcraft-python"
 
 [tool.setuptools.dynamic]
-readme = {file = ["README.md"]}
+readme = {file = ["README.rst"]}
 
 [tool.setuptools.packages.find]
 where = ["src"]