Cleanup (ver/1.20.2) (#77)

* Cleanup README.md

Signed-off-by: Alpha <dev@alpha93.kr>

* what

Signed-off-by: Alpha <dev@alpha93.kr>

* Remove unused files

---------

Signed-off-by: Alpha <dev@alpha93.kr>

.github/workflows/close-invalid-prs.yml

@@ -1,14 +0,0 @@
-name: Close invalid PRs
-
-on:
-  pull_request_target:
-    types: [ opened ]
-
-jobs:
-  run:
-    if: ${{ github.repository != github.event.pull_request.head.repo.full_name && !startsWith(github.head_ref, 'ver/') }}
-    runs-on: ubuntu-22.04
-    steps:
-      - uses: superbrothers/close-pull-request@v3
-        with:
-          comment: "Please do not open pull requests from the `master` branch, create a new branch instead."