Update standard workflow files. (#420)

* build: Creating a missing workflow file `self-assign-issue.yml`.

The .github/workflows/self-assign-issue.yml workflow is missing or needs an update to stay in
sync with the current standard for this workflow as defined in the
`.github` repo of the `openedx` GitHub org.

* build: Creating a missing workflow file `add-remove-label-on-comment.yml`.

The .github/workflows/add-remove-label-on-comment.yml workflow is missing or needs an update to stay in
sync with the current standard for this workflow as defined in the
`.github` repo of the `openedx` GitHub org.

* build: Updating a missing workflow file `add-depr-ticket-to-depr-board.yml`.

The .github/workflows/add-depr-ticket-to-depr-board.yml workflow is missing or needs an update to stay in
sync with the current standard for this workflow as defined in the
`.github` repo of the `openedx` GitHub org.

.github/workflows/add-depr-ticket-to-depr-board.yml

@@ -16,4 +16,4 @@ jobs:
     secrets:
       GITHUB_APP_ID: ${{ secrets.GRAPHQL_AUTH_APP_ID }}
       GITHUB_APP_PRIVATE_KEY: ${{ secrets.GRAPHQL_AUTH_APP_PEM }}
-      SLACK_BOT_TOKEN: ${{ secrets.SLACK_ISSUE_BOT_TOKEN }}
+      SLACK_BOT_TOKEN: ${{ secrets.SLACK_ISSUE_BOT_TOKEN }}

.github/workflows/add-remove-label-on-comment.yml

@@ -0,0 +1,20 @@
+# This workflow runs when a comment is made on the ticket
+# If the comment starts with "label: " it tries to apply
+# the label indicated in rest of comment.
+# If the comment starts with "remove label: ", it tries
+# to remove the indicated label.
+# Note: Labels are allowed to have spaces and this script does
+# not parse spaces (as often a space is legitimate), so the command
+# "label: really long lots of words label" will apply the
+# label "really long lots of words label"
+
+name: Allows for the adding and removing of labels via comment
+
+on:
+  issue_comment:
+    types: [created]
+
+jobs:
+  add_remove_labels:
+    uses: openedx/.github/.github/workflows/add-remove-label-on-comment.yml@master
+

.github/workflows/self-assign-issue.yml

@@ -0,0 +1,12 @@
+# This workflow runs when a comment is made on the ticket
+# If the comment starts with "assign me" it assigns the author to the
+# ticket (case insensitive)
+
+name: Assign comment author to ticket if they say "assign me"
+on:
+  issue_comment:
+    types: [created]
+
+jobs:
+  self_assign_by_comment:
+    uses: openedx/.github/.github/workflows/self-assign-issue.yml@master