Add SemVer compatibility checks

This integrates the cargo-semver-checks tool in the CI to check for
SemVer compatibility as per the Cargo reference
(https://doc.rust-lang.org/cargo/reference/semver.html).

The cargo-public-api tool is a viable alternative to
cargo-semver-checks, but I didn't choose it because its comparison
baseline needs to be stored in the repository and manually updated on
each change. For zenoh, the 1.0.0 revision will be the baseline for the
forseeable future.

This comes with a caveat though: cargo-semver-checks accepts a "release
type" argument which would be either patch or minor in zenoh's case. I
specified "patch" since I expect patch releases to be more common. If
minor API compatibility (as defined by the Cargo reference) are
expected, then the CI workflow would need to be manually adjusted at the
start and the end of the release cycle.

.github/workflows/ci.yml

@@ -51,6 +51,9 @@ jobs:
       - name: Install latest cargo-machete
         uses: taiki-e/install-action@cargo-machete
 
+      - name: Install latest cargo-semver-checks
+        uses: taiki-e/install-action@cargo-semver-checks
+
       - name: Code format check
         run: cargo fmt --check -- --config "unstable_features=true,imports_granularity=Crate,group_imports=StdExternalCrate"
 
@@ -100,6 +103,9 @@ jobs:
       - name: Check unused dependencies
         run: cargo machete
 
+      - name: Check SemVer Compatibility
+        run: cargo semver-checks --verbose --default-features --baseline-rev 1.0.0 --package zenoh --release-type patch
+
   test:
     name: Unit tests on ${{ matrix.os }}
     runs-on: ${{ matrix.os }}