fix broken URLs and automate broken URL checks #70

This commit:
- Fixes broken URLs using archive.org or other references.
- Replaces tenforums.com URLs with better documentation as they tend to return HTTP status code 403 to tests and also are low quality source.
- Changes all insecure http sources to https alternatives
- Adds integration tests to check for broken URLs
  - There's logic implemented for having a delay inbetween when sending requests to same domains, however it's not used as the sources can respond to totally parallelized requests.
- Run test pipeline weekly to get notified about broken URls without commits

.github/workflows/test.yaml

@@ -1,6 +1,10 @@
 name: Test
 
-on: [ push, pull_request ]
+on:
+  push:
+  pull_request:
+  schedule: # for integration tests
+    - cron: '0 0 * * 0' # at 00:00 on every Sunday
 
 jobs:
   run-tests: