Github CI Actions workflows just on PR to main

Author: J-Rios

.github/workflows/build_avr.yml

@@ -1,6 +1,9 @@
 name: Build AVR CI
 
-on: [push]
+on:
+  pull_request:
+    branches:
+      - main
 
 jobs:
   build_avr:

.github/workflows/build_linux.yml

@@ -1,6 +1,9 @@
 name: Build Linux CI
 
-on: [push]
+on:
+  pull_request:
+    branches:
+      - main
 
 jobs:
   build_linux:

.github/workflows/build_pio_arduino.yml

@@ -1,6 +1,9 @@
 name: Build PlatformIO Arduino CI
 
-on: [push]
+on:
+  pull_request:
+    branches:
+      - main
 
 jobs:
   build_pio_arduino:

.github/workflows/build_pio_espidf.yml

@@ -1,6 +1,9 @@
 name: Build PlatformIO ESP-IDF CI
 
-on: [push]
+on:
+  pull_request:
+    branches:
+      - main
 
 jobs:
   build_pio_espidf: