Add release-making instructions

Author: elprans

.github/RELEASING.rst

@@ -0,0 +1,55 @@
+Releasing asyncpg
+=================
+
+When making an asyncpg release follow the below checklist.
+
+1. Remove the ``.dev0`` suffix from ``__version__`` in ``asyncpg/__init__.py``.
+
+2. Make a release commit:
+
+   .. code-block:: shell
+
+      $ git commit -a -m "asyncpg vX.Y.0"
+
+   Here, X.Y.0 is the ``__version__`` in ``asyncpg/__init__.py``.
+
+3. Force push into the "releases" branch on Github:
+
+   .. code-block:: shell
+
+      $ git push --force origin master:releases
+
+4. Wait for CI to make the release build.  If there are errors,
+   investigate, fix and repeat steps 2 through 4.
+
+5. Prepare the release changelog by cleaning and categorizing the output of
+   ``.github/release_log.py``.  Look at previous releases for examples
+   of changelog formatting:
+
+   .. code-block:: shell
+
+      $ .github/release_log.py <previously-released-version-tag>
+
+6. Make an annotated, signed git tag and use the changelog as the tag
+   annotation:
+
+   .. code-block:: shell
+
+      $ git tag -s vX.Y.0
+      <paste changelog>
+
+7. Push the release commit and the new tag to master on Github:
+
+   .. code-block:: shell
+
+      $ git push --follow-tags
+
+8. Wait for CI to publish the build to PyPI.
+
+9. Edit the release on Github and paste the same content you used for
+   the tag annotation (Github treats tag annotations as plain text,
+   rather than Markdown.)
+
+10. Open master for development by bumping the minor component of
+    ``__version__`` in ``asyncpg/__init__.py`` and appending the ``.dev0``
+    suffix.