feat: update version to 0.6.9 and add packaging for Linux and BSD

- Bump version from 0.6.8 to 0.6.9 in Cargo.toml and Cargo.lock.
- Enhance GitHub Actions workflow to build and publish .deb, .rpm, and Snap packages.
- Implement AUR publishing for both dcr and dcr-bin packages.
- Add support for workspace-only projects in the build system.
- Introduce new `workspace` flag for build and run commands.
- Create snapcraft.yaml for Snap package configuration.
- Update build.rs and related files to handle workspace members and inheritance.
- Modify config handling to support optional package and build configurations.

packaging/snap/snapcraft.yaml

@@ -0,0 +1,18 @@
+name: dcr
+base: core22
+version: '0.6.9'
+summary: Cargo-like utility to manage C/C++ projects
+description: |
+  A build tool and package manager for C/C++ projects inspired by Rust's Cargo.
+
+grade: stable
+confinement: classic
+
+apps:
+  dcr:
+    command: bin/dcr
+
+parts:
+  dcr:
+    plugin: dump
+    source: ../../dist/