docs: add tags

Author: VChet

package.json

@@ -12,6 +12,7 @@
     "type": "git",
     "url": "git+https://github.com/VChet/git-merged-branches.git"
   },
+  "tags": ["git", "cli", "branch", "issue-tracker"],
   "bugs": {
     "url": "https://github.com/VChet/git-merged-branches/issues"
   },