ci: add back required workflow to repo (#1279)

### Summary of Changes

Organization-wide required workflows are currently too strict (see [this
discussion](community/community#43890)).
I've disabled them for now and instead added them back directly to the
repo.

Author: lars-reimann

.github/workflows/dependency-review.yml

@@ -0,0 +1,11 @@
+name: Dependency Review
+
+on:
+  pull_request:
+    branches: [main]
+  merge_group:
+
+jobs:
+  dependency-review:
+    if: ${{ github.event_name == 'pull_request' }}
+    uses: lars-reimann/.github/.github/workflows/dependency-review-reusable.yml@main

.github/workflows/megalinter.yml

@@ -0,0 +1,13 @@
+name: MegaLinter
+
+on:
+  pull_request:
+    branches: [main]
+  merge_group:
+
+jobs:
+  megalinter:
+    if: ${{ github.event_name == 'pull_request' }}
+    uses: lars-reimann/.github/.github/workflows/megalinter-reusable.yml@main
+    secrets:
+      PAT: ${{ secrets.PAT }}

.github/workflows/pr-format.yml

@@ -0,0 +1,15 @@
+name: Pull Request Format
+
+on:
+  pull_request_target:
+    types:
+      - opened
+      - edited
+      - synchronize
+      - reopened
+  merge_group:
+
+jobs:
+  check-format:
+    if: ${{ github.event_name == 'pull_request' }}
+    uses: lars-reimann/.github/.github/workflows/pr-format-reusable.yml@main