Prevent duplicate CI runs, also work with PRs from forks (#1443)

* Prevent duplicate CI runs

* Trigger CI on pull requests from forks

Author: kiendang

.github/workflows/lint.yml

@@ -1,6 +1,9 @@
 name: Lint
 
-on: [push, pull_request]
+on:
+  push:
+    branches: ["main"]
+  pull_request:
 
 jobs:
   build:

.github/workflows/tests.yml

@@ -1,6 +1,9 @@
 name: Tests
 
-on: [push, pull_request]
+on:
+  push:
+    branches: ["main"]
+  pull_request:
 
 jobs:
   build: