Add a cron schedule in actions per month to create artifacts without any commit

at 2023-02-01 00:00:00
then at 2023-03-01 00:00:00
then at 2023-04-01 00:00:00
then at 2023-05-01 00:00:00
then at 2023-06-01 00:00:00
...

Co-Authored-By: Elad Salomons <selad@optiwater.com>

.github/workflows/ccpp.yml

@@ -1,6 +1,10 @@
 name: linux
 
-on: [push]
+on: 
+  push:
+  pull_request: 
+  schedule: 
+    - cron: '0 0 1 * *'
 
 jobs:
   build:

.github/workflows/win32.yml

@@ -1,6 +1,10 @@
 name: epanet2-win32
 
-on: [push]
+on: 
+  push:
+  pull_request: 
+  schedule: 
+    - cron: '0 0 1 * *'
 
 jobs:
   build:

.github/workflows/win64.yml

@@ -1,6 +1,10 @@
 name: epanet2-win64
 
-on: [push]
+on: 
+  push:
+  pull_request: 
+  schedule: 
+    - cron: '0 0 1 * *'
 
 jobs:
   build: