Add GitHub configuration files

.github/workflows/CODEOWNERS

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+* @marco-compiler/reviewers

.github/workflows/workflows/fast-forward.yml

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+name: fast-forward
+on:
+  issue_comment:
+    types: [created, edited]
+jobs:
+  fast-forward:
+    # Only run if the comment contains the /fast-forward command.
+    if: ${{ contains(github.event.comment.body, '/fast-forward')
+      && github.event.issue.pull_request }}
+    runs-on: ubuntu-latest
+
+    permissions:
+      contents: write
+      pull-requests: write
+      issues: write
+
+    steps:
+      - name: Fast forwarding
+        uses: sequoia-pgp/fast-forward@v1
+        with:
+          merge: true
+          comment: on-error

.github/workflows/workflows/pr-clang-format.yml

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+name: "Check code formatting"
+
+permissions:
+  contents: read
+
+on: pull_request
+
+jobs:
+  clang-format:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Fetch source
+        uses: actions/checkout@v4
+        with:
+          ref: ${{ github.event.pull_request.head.sha }}
+
+      - name: Get changed files
+        id: changed-files
+        uses: tj-actions/changed-files@v44
+        with:
+          files: |
+            **/*.{h,c,cpp}
+          separator: " "
+
+      - name: List changed files
+        env:
+          CHANGED_FILES: ${{ steps.changed-files.outputs.all_changed_files }}
+        run: |
+          echo "Changed files:"
+          echo "$CHANGED_FILES"
+
+      - name: Install clang-format
+        uses: aminya/setup-cpp@v1
+        with:
+          clangformat: true
+
+      - name: Check format
+        env:
+          CHANGED_FILES: ${{ steps.changed-files.outputs.all_changed_files }}
+        run: |
+          clang-format --dry-run --style=file --Werror --verbose $CHANGED_FILES