Rename workflow file

Because build is a bad name for a workflow that doesn't build anything

.forgejo/workflows/check.yaml

@@ -0,0 +1,33 @@
+---
+on: [push]
+
+name: CI
+
+jobs:
+  formatting:
+    name: Formatting
+    runs-on: ubuntu-22.04
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+      - name: Set up Rust
+        uses: https://github.com/dtolnay/rust-toolchain@nightly
+        with:
+          components: rustfmt
+      - name: Check Rust formatting
+        run: cargo fmt --all -- --check
+
+  clippy:
+    name: Clippy
+    runs-on: ubuntu-22.04
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+      - name: Set up Rust
+        uses: https://github.com/dtolnay/rust-toolchain@nightly
+        with:
+          components: clippy
+      - name: Install dependencies
+        uses: ./.forgejo/actions/install-system-libraries
+      - name: Run Clippy
+        run: cargo clippy -- -D warnings