chore(ci) : Deploy to staging through a PR label

It is annoying to be competing with each other when pushing code, so I
feel like it's going to help if we decide to deploy through adding a
non-mandatory label than "all the time unless draft".

Also, drafts are something different, at least for me ^^

.github/workflows/build_deploy.yml

@@ -9,14 +9,13 @@ on:
     branches: [main]
   pull_request:
     branches: [main]
-    # default types + ready_for_review
-    types: [opened, synchronize, repopened, ready_for_review]
+    types: [opened, synchronize, reopened, ready_for_review, labeled]
 
 jobs:
   build:
     runs-on: ubuntu-latest
 
-    if: ${{ !(github.event_name == 'pull_request' && github.event.pull_request.draft) }}
+    if: contains(github.event.pull_request.labels.*.name, 'deploy-to-staging')
 
     strategy:
       matrix: