build(deps-dev): remove package rollup-plugin-license (#1796)

The `rollup-plugin-license` has been using too many deprecated dependencies, so it is necessary to remove it.

As an alternative, this changes uses Rollup `output.banner` to insert copyright information. Since `terser` runs after `output`, it is not possible to insert the Front Matter defining permlink for `sw.js` through the same way (Jekyll Front Matter is YAML rather than JS, which would cause errors with terser).

Therefore, _Jekyll Collection_ is now used to add permlink to `sw.js`, with the collection named `app`, and the directory placed in `_app`. This directory is not tracked by git, but it will be included when building the gem.

package.json

@@ -8,6 +8,7 @@
   },
   "author": "Cotes Chung",
   "license": "MIT",
+  "since": 2019,
   "bugs": {
     "url": "https://github.com/cotes2020/jekyll-theme-chirpy/issues"
   },
@@ -43,7 +44,6 @@
     "husky": "^9.0.11",
     "purgecss": "^6.0.0",
     "rollup": "^4.18.0",
-    "rollup-plugin-license": "^3.4.0",
     "semantic-release": "^24.0.0",
     "stylelint": "^16.6.1",
     "stylelint-config-standard-scss": "^13.1.0"