Markdown linter (#1309)

* Add markdown linting

- add linter default rules
- adapt rules to current code
- fix the code for linting to pass
- add CI check

fix #1243

* Fix markdown for Substrate
* Fix tooling install
* Fix workflow
* Add documentation
* Remove trailing spaces
* Update .github/.markdownlint.yaml

Co-authored-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>
* Fix mangled markdown/lists
* Fix captalization issues on known words

cumulus/scripts/ci/changelog/README.md

@@ -0,0 +1,77 @@
+# Changelog
+
+Currently, the changelog is built locally. It will be moved to CI once labels stabilize.
+
+For now, a bit of preparation is required before you can run the script:
+- fetch the srtool digests
+- store them under the `digests` folder as `<chain>-srtool-digest.json`
+- ensure the `.env` file is up to date with correct information
+
+The content of the release notes is generated from the template files under the `scripts/ci/changelog/templates` folder.
+For readability and maintenance, the template is split into several small snippets.
+
+Run:
+```
+./bin/changelog <ref_since> [<ref_until>=HEAD]
+```
+
+For instance:
+```
+./bin/changelog parachains-v7.0.0-rc8
+```
+
+A file called `release-notes.md` will be generated and can be used for the release.
+
+## ENV
+
+You may use the following ENV for testing:
+
+```
+RUSTC_STABLE="rustc 1.56.1 (59eed8a2a 2021-11-01)"
+RUSTC_NIGHTLY="rustc 1.57.0-nightly (51e514c0f 2021-09-12)"
+PRE_RELEASE=true
+HIDE_SRTOOL_ROCOCO=true
+HIDE_SRTOOL_SHELL=true
+REF1=statemine-v5.0.0
+REF2=HEAD
+DEBUG=1
+NO_CACHE=1
+```
+
+By default, the template will include all the information, including the runtime data. For clients releases, we don't
+need those and they can be skipped by setting the following env:
+```
+RELEASE_TYPE=client
+```
+
+## Considered labels
+
+The following list will likely evolve over time and it will be hard to keep it in sync. In any case, if you want to find
+all the labels that are used, search for `meta` in the templates. Currently, the considered labels are:
+
+- Priority: C<N> labels
+- Audit: D<N> labels
+- E4 => new host function
+- B0 => silent, not showing up
+- B1-releasenotes (misc unless other labels)
+- B5-client (client changes)
+- B7-runtimenoteworthy (runtime changes)
+- T6-XCM
+
+Note that labels with the same letter are mutually exclusive. A PR should not have both `B0` and `B5`, or both `C1` and
+`C9`. In case of conflicts, the template will decide which label will be considered.
+
+## Dev and debuggin
+
+### Hot Reload
+
+The following command allows **Hot Reload**:
+```
+fswatch templates -e ".*\.md$" | xargs -n1 -I{} ./bin/changelog statemine-v5.0.0
+```
+### Caching
+
+By default, if the changelog data from Github is already present, the calls to the Github API will be skipped and the
+local version of the data will be used. This is much faster. If you know that some labels have changed in Github, you
+probably want to refresh the data. You can then either delete manually the `cumulus.json` file or `export NO_CACHE=1` to
+force refreshing the data.