chore: omit lockfile from release commit (#126)

Turns out ignoring `.gitignore` while adding files to the release commit is a feature not a bug so specify the list of files to add.

Refs: semantic-release/git#56

We can probably revert if semantic-release/git#527 ever gets merged.

Author: achingbrain

package.json

@@ -142,7 +142,9 @@
       "@semantic-release/changelog",
       "@semantic-release/npm",
       "@semantic-release/github",
-      "@semantic-release/git"
+      ["@semantic-release/git", {
+        "assets": ["CHANGELOG.md", "package.json"]
+      }]
     ]
   },
   "scripts": {