ci: Activate all features when building docs — heartwood

Currently, cargo doc fails on warnings for missing links to qcheck and radicle_git_ref_format. This will enable the required features to compile those modules in.

       export PATH="/root/.cargo/bin:$PATH"
       export RUSTDOCFLAGS='-D warnings'
       cargo doc --workspace --no-deps
       cargo doc --workspace --no-deps --all-features
   # Prepare source tree for building a Debian package.
   - action: shell

   cargo fmt --check
   cargo clippy --all-targets --workspace -- --deny warnings
   cargo build --all-targets --workspace
   cargo doc --workspace --no-deps
   cargo doc --workspace --no-deps --all-features
   cargo test --workspace --no-fail-fast