chore: avoid duplicate actions runs

As explained here:

- https://wildwolf.name/github-actions-how-to-avoid-running-the-same-workflow-multiple-times/

Before:

- If I pushed to a branch, without making a PR, actions would run once.
- If I pushed to a branch, then opened a PR, actions would run twice.
- If somebody else opened a PR (from a fork), actions would run once.

After:

- If I push to a branch, without making a PR, actions will run once.
- If I push to a branch, then open a PR, actions will run once (ie. due
  to the push, not the PR).
- If somebody else opens a PR (from a fork), actions will run once.

Author: wincent

.github/workflows/lua.yml

@@ -1,8 +1,17 @@
 name: lua
-on: [push, pull_request]
+
+on:
+  push:
+    branches:
+      - '**'
+  pull_request:
+    branches:
+      - '**'
+
 jobs:
   style:
     runs-on: ubuntu-latest
+    if: github.event_name != 'pull_request' || github.event.pull_request.head.repo.full_name != github.event.pull_request.base.repo.full_name
     steps:
       - uses: actions/checkout@v2
       - uses: JohnnyMorganz/stylua-action@1.0.0
@@ -17,6 +26,7 @@ jobs:
 
   test:
     runs-on: ubuntu-latest
+    if: github.event_name != 'pull_request' || github.event.pull_request.head.repo.full_name != github.event.pull_request.base.repo.full_name
     steps:
       - uses: actions/checkout@v2
       - uses: leafo/gh-actions-lua@v9

.github/workflows/prettier.yml

@@ -1,8 +1,17 @@
 name: prettier
-on: [push, pull_request]
+
+on:
+  push:
+    branches:
+      - '**'
+  pull_request:
+    branches:
+      - '**'
+
 jobs:
   style:
     runs-on: ubuntu-latest
+    if: github.event_name != 'pull_request' || github.event.pull_request.head.repo.full_name != github.event.pull_request.base.repo.full_name
     steps:
       - uses: actions/checkout@v2
       - uses: actionsx/prettier@v2

.github/workflows/ruby.yaml

@@ -1,8 +1,17 @@
 name: ruby
-on: [push, pull_request]
+
+on:
+  push:
+    branches:
+      - '**'
+  pull_request:
+    branches:
+      - '**'
+
 jobs:
   style:
     runs-on: ubuntu-latest
+    if: github.event_name != 'pull_request' || github.event.pull_request.head.repo.full_name != github.event.pull_request.base.repo.full_name
     steps:
       - uses: actions/checkout@v2
       - uses: jidicula/clang-format-action@v4.8.0
@@ -12,6 +21,7 @@ jobs:
 
   test:
     runs-on: ubuntu-latest
+    if: github.event_name != 'pull_request' || github.event.pull_request.head.repo.full_name != github.event.pull_request.base.repo.full_name
     steps:
       - uses: actions/checkout@v2
       - name: Install libraries