Implement spellcheck action for markdown

[tmsdkeys]

Ensure that spellcheck is performed before documentation is added to gitbook.

Note that given the documentation workflow (some maintained in gitbook-docs, some in nexus-sdk and nexus-next) there's different points where content is checked.

[tmsdkeys]

Traditional (i.e. pre AI) spellcheckers broadly work in one of two ways:

1. typos style: keep a dictionary of spelling mistakes and cross-reference

• Pro: lightweight and reduces false positives
• Con: will miss some errors

2. cspell style: keep a dictionary of correct words and cross-reference

• Pro: Pretty good at catching errors
• Con: more false positives, especially when jargon is used and takes more work

AI and LLMs have changed the game for language checks:

• they have more context awareness
• they can capture grammar mistakes as well

Example: Spellcaster

• Pro: Has a GH action that integrates AI language checks (and code samples)
• Con: Have to add API key for the GH action

Recommendation: Given that most devs will have access to an integrated LLM inside their IDE, I would propose a hybrid option:

1. Document the recommendation of using integrated LLM to check language mistakes when pushing markdown files
2. Add lightweight typos GH action as an extra check in CI/CD

This solution finds a balance between using modern AI features during writing docs in IDE + some extra automated checks.