enable github app integration for slash commands (#832)

.github/workflows/slash-beekeeper.yml

 name: Slash Beekeeper
 
 on:
-  issue_comment:
-    types: [created]
+  repository_dispatch:
+    types: [beekeeper]
 
 jobs:
   beekeeper:
-    name: Execute "/beekeeper" slash command
-    if: github.event.issue.pull_request != '' && contains(github.event.comment.body, '/beekeeper')
+    name: Execute "/run beekeeper" slash command
     env:
       REPLICA: 3
     runs-on: ubuntu-latest
     steps:
-      - name: Check for Command
-        id: command
-        uses: xt0rted/slash-command-action@v1
-        with:
-          repo-token: ${{ secrets.GITHUB_TOKEN }}
-          command: beekeeper
-          reaction-type: "rocket"
-      - name: Get PR Branch
-        if: steps.command.outputs.command-name == 'beekeeper'
-        id: comment-branch
-        uses: xt0rted/pull-request-comment-branch@v1
-        with:
-          repo_token: ${{ secrets.GITHUB_TOKEN }}
-      - name: Echo command (debug)
-        run: echo "The command was '${{ steps.command.outputs.command-name }}' with arguments '${{ steps.command.outputs.command-arguments }}'"
       - name: Checkout
         uses: actions/checkout@v2
         with:
-          ref: ${{ steps.comment-branch.outputs.ref }}
+          ref: ${{ github.event.client_payload.ref }}
           fetch-depth: 1
       - name: Install bee-local
         run: |