Add checksum file creation to releases: (#187)

## Description

<!--- Please describe what this PR is going to change -->
This makes it safer for users to consume Hook tarballs. Will also help
the user experience in the charts repo.

## Why is this needed

<!--- Link to issue you have raised -->

Fixes: #168 

## How Has This Been Tested?
<!--- Please describe in detail how you tested your changes. -->
<!--- Include details of your testing environment, and the tests you ran
to -->
<!--- see how your change affects other areas of the code, etc. -->


## How are existing users impacted? What migration steps/scripts do we
need?

<!--- Fixes a bug, unblocks installation, removes a component of the
stack etc -->
<!--- Requires a DB migration script, etc. -->


## Checklist:

I have:

- [ ] updated the documentation and/or roadmap (if required)
- [ ] added unit or e2e tests
- [ ] provided instructions on how to upgrade

.github/workflows/ci.yaml

@@ -106,12 +106,20 @@ jobs:
           tag: latest
           message: "Latest development build"
 
+      - name: Generate checksum
+        uses: jmgilman/actions-generate-checksum@v1
+        with:
+          method: sha512
+          patterns: hook_*.tar.gz
+
       - name: Update latest release
         uses: softprops/action-gh-release@v1
         with:
           name: Hook Latest Development Build
           body: ${{env.RELEASE_NOTES}}
-          files: hook_*.tar.gz
+          files: |
+            hook_*.tar.gz
+            checksum.txt
           prerelease: true
           tag_name: latest
 
@@ -139,8 +147,16 @@ jobs:
         env:
           GITHUB_TOKEN: ${{secrets.GITHUB_TOKEN}}
 
+      - name: Generate checksum
+        uses: jmgilman/actions-generate-checksum@v1
+        with:
+          method: sha512
+          patterns: hook_*.tar.gz
+
       - name: Update latest release
         uses: softprops/action-gh-release@v1
         with:
           body: ${{env.RELEASE_NOTES}}
-          files: hook_*.tar.gz
+          files: |
+            hook_*.tar.gz
+            checksum.txt