ci: Make flank release more automatically (#1352)

Fixes #1346 

## Test Plan
> How do we know the code works?

1. Create release notes job (this which generates documentation and changelog) will run each 1st day of the month
2. After merge Pr with changelog
3. Flank-release bot will push the tag with next version to repository
4. Then release job will run as usual

## Checklist

- [x] Documented
- [x] At schedule to run release job at 1st day of the month
- [x] Create job which will push release tag after merge PR

.github/workflows/create_new_release.yml

@@ -0,0 +1,34 @@
+name: Create new release
+
+on:
+  pull_request:
+    types: [ closed ]
+
+jobs:
+  create_release:
+    runs-on: ubuntu-latest
+    if: github.event.pull_request.merged == true && contains(github.event.pull_request.labels.*.name, 'release') && contains(github.event.pull_request.user.login, 'flank-release[bot]') && contains(github.event.pull_request.title, 'release notes for')
+    steps:
+      - uses: actions/checkout@v2
+      - uses: tibdex/github-app-token@v1
+        id: generate-token
+        with:
+          app_id: ${{ secrets.FLANK_RELEASE_APP_ID }}
+          private_key: ${{ secrets.FLANK_RELEASE_PRIVATE_KEY }}
+
+      - name: Gradle Build flankScripts and add it to PATH
+        run: |
+          ./flank-scripts/bash/buildFlankScripts.sh
+          echo "./flank-scripts/bash" >> $GITHUB_PATH
+      - name: Set next release tag variable
+        run: |
+          TAG=$(flankScripts ci nextReleaseTag --token=${{ secrets.GITHUB_TOKEN }})
+          echo "NEXT_RELEASE_TAG=$(echo $TAG)" >> $GITHUB_ENV
+          
+      - name: Push tag
+        id: tag_version
+        uses: mathieudutour/github-tag-action@v5
+        with:
+          github_token: ${{ steps.generate-token.outputs.token }}
+          custom_tag: ${{ env.NEXT_RELEASE_TAG }}
+          tag_prefix: '' 

.github/workflows/release_notes_generation.yml

@@ -2,6 +2,8 @@ name: "Generate release notes for next commit"
 
 on: 
   workflow_dispatch:
+  schedule:
+    - cron: 0 7 1 * *
 
 jobs:
   generateReleaseNotes:

docs/release_process.md

@@ -16,12 +16,19 @@ Each push:
 - to `master` branch run Snapshot release
 - of tag `v*` run regular release
 
-## Manual Steps
+## Triggering release 
+
+### Manually
 1. Navigate to [Github Actions](https://github.com/Flank/flank/actions)
 2. Run job [`Generate release notes for next commit`](https://github.com/Flank/flank/actions?query=workflow%3A%22Generate+release+notes+for+next+commit%22) by using `Run Workflow` button
-3. After merging, push a tag for the release
+3. After merging PR,  the next tag will be pushed to repository
 4. Wait for CI job to finish
 
+### Automatically
+1. Release job will run each 1st day of month
+2. After merging PR,  the next tag will be pushed to repository
+2. Wait for CI job to finish
+
 ## CI Steps
 1. Gradle Build flankScripts and add it to PATH
 2. Set environment variables