feat: register proposal via deep links

[maxwellmattryan]

Summary

Please summarize your changes, describing what they are and why they were made.

Users will need to be able to register proposals via deep links on various websites.

Changelog

- Add Governance deep link context with initial "register proposal" operation 
- Update handbook documentation accordingly

Relevant Issues

Please list any related issues using development keywords.

Closees #4865

Testing

Platforms

Please select any platforms where your changes have been tested.

• Desktop
  • MacOS
  • Linux
  • Windows
• Mobile
  • iOS
  • Android

Instructions

Please describe the specific instructions, configurations, and/or test cases necessary to test and verify that your changes work as intended.

Tested various valid and invalid deep links.

Checklist

Please tick all of the following boxes that are relevant to your changes.

• I have followed the contribution guidelines for this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have added or modified tests that prove my changes work as intended
• I have verified that new and existing unit tests pass locally with my changes
• I have verified that my latest changes pass CI workflows for testing and linting
• I have made corresponding changes to the documentation

[Tuditi]

LGTM! 🔥