Add BOT_APPROVED_FILES (#441)

# Motivation

Starting soon, files changed by bots must be listed in
`.github/repo_policies/BOT_APPROVED_FILES`.

# Changes

1. I looked at recent PRs made by bots and added the files changed by
them to `.github/repo_policies/BOT_APPROVED_FILES`.
2. Made bot PRs easier to spot in the future by prepending "bot: " to
their titles, like we do in nns-dapp.

.github/repo_policies/BOT_APPROVED_FILES

@@ -0,0 +1,3 @@
+bin/versions.bash
+dfx.json
+dfx.json.original

.github/workflows/update-dfx.yml

@@ -41,7 +41,7 @@ jobs:
             echo An update is available for dfx.
             git diff
             echo "updated=1" >> "$GITHUB_OUTPUT"
-            echo "title=Update dfx to version $latest_dfx_version" >> "$GITHUB_OUTPUT"
+            echo "title=bot: Update dfx to version $latest_dfx_version" >> "$GITHUB_OUTPUT"
           else
             echo "updated=0" >> "$GITHUB_OUTPUT"
           fi

.github/workflows/update-ic.yml

@@ -64,7 +64,7 @@ jobs:
           author: gix-bot <[email protected]>
           branch: bot-ic-update
           delete-branch: true
-          title: 'Update IC commit'
+          title: 'bot: Update IC commit'
           # Since the this is a scheduled job, a failure won't be shown on any
           # PR status. To notify the team, we send a message to our Slack channel on failure.
       - name: Notify Slack on failure