Initial implementation of breadpaper

CLI tool that sets a wallpaper with awww, generates a pywal colour
palette, and reloads bread-theme to recolour all running bread GTK apps.
Includes CI workflows, bakery metadata, and Arch PKGBUILD.

.github/workflows/ci.yml

@@ -0,0 +1,38 @@
+name: CI
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+  workflow_dispatch:
+
+env:
+  CARGO_TERM_COLOR: always
+  RUSTFLAGS: "-D warnings"
+
+jobs:
+  test:
+    name: fmt · clippy · test · build
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Install Rust toolchain
+        uses: dtolnay/rust-toolchain@stable
+        with:
+          components: rustfmt, clippy
+
+      - name: Cache cargo
+        uses: Swatinem/rust-cache@v2
+
+      - name: Format check
+        run: cargo fmt --all -- --check
+
+      - name: Clippy
+        run: cargo clippy --all-targets -- -D warnings
+
+      - name: Test
+        run: cargo test --all --verbose
+
+      - name: Release build
+        run: cargo build --release --verbose