docs: update documentation links (#3459)

# What does this PR do?
* Updates documentation links from readthedocs to llamastack.github.io

## Test Plan
* Manual testing

.github/ISSUE_TEMPLATE/config.yml

@@ -2,10 +2,10 @@ blank_issues_enabled: false
 
 contact_links:
   - name: Have you read the docs?
-    url: https://llama-stack.readthedocs.io/en/latest/index.html
+    url: https://llamastack.github.io/latest/providers/external/index.html
     about: Much help can be found in the docs
   - name: Start a discussion
-    url: https://github.com/meta-llama/llama-stack/discussions/new
+    url: https://github.com/llamastack/llama-stack/discussions/new/
     about: Start a discussion on a topic
   - name: Chat on Discord
     url: https://discord.gg/llama-stack