Add changelog generation (#761)

* WIP Release notes generation and templates

* WIP Add new sections to the template

* WIP renaming and wip

* Fix runtime template

* Add doc, NO_CACHE and tweaking of the templates

* Renaming cl into cumulus to make room for the polkadot and substrate

* Fetch data from Substrate and Polkadot

* WIP convert bash script to ruby

* Convert to Ruby

* Fix host function delection

* Extract priority to a macro

* Fix misc changes

* Draft release workflow

* Fix runtime dir

* Add ENV to ignore runtimes

* Install tooling separately

* WIP troubleshooting - remove sudo

* Minor formatting fixes

* Fix workflow

* Add missing dep

* Linting

* Fix changelog script

* Add missing tera install

* Use absolute paths

* Fix path + cleanup

* Fix changelog generation

* Add missing pre-release ENV

* Fix rust version ENV

* Fix release notes path

* Fix output

* Fix runtime_dir for cumulus

* Fix ENV substitutions

* Fix styling

* Debugging

* Styling

* Fix call to fetch the runtime version

* Cleanup and doc

* Delete sample .env

* Update scripts/changelog/templates/change.md.tera

Co-authored-by: Alexander Popiak <alexander.popiak@parity.io>

* Change XCM emoji marker for a ✉️

Co-authored-by: Alexander Popiak <alexander.popiak@parity.io>

cumulus/scripts/changelog/templates/runtimes.md.tera

@@ -0,0 +1,17 @@
+{# This include shows the list and details of the runtimes #}
+{%- import "runtime.md.tera" as m_r -%}
+
+## Runtimes
+
+{% set rtm = srtool[0] -%}
+
+The information about the runtimes included in this release can be found below.
+The runtimes have been built using [{{ rtm.data.gen }}](https://github.com/paritytech/srtool) and `{{ rtm.data.rustc }}`.
+
+{%- for runtime in srtool | sort(attribute="name") %}
+{%- set HIDE_VAR = "HIDE_SRTOOL_" ~ runtime.name | upper %}
+{%- if not env is containing(HIDE_VAR) %}
+
+{{ m_r::runtime(runtime=runtime) }}
+{%- endif %}
+{%- endfor %}