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

substrate/frame/system/benchmarking/README.md

@@ -1 +1 @@
-License: Apache-2.0
+License: Apache-2.0

substrate/frame/system/benchmarking/res/README.md

@@ -2,4 +2,5 @@ These runtimes are used for benchmarking the `set_code` intrinsic.
 
 **Don't use them in production environments!**
 
-To update the just copy the new runtime from `target/release/wbuild/kitchensink-runtime/kitchensink_runtime.compact.compressed.wasm` to here.
+To update the just copy the new runtime from
+`target/release/wbuild/kitchensink-runtime/kitchensink_runtime.compact.compressed.wasm` to here.