feat: complete NIP-11 relay info parity

[a-khushal]

this pr improves nip-11 support in nostream. it adds some missing relay info fields, required cors headers, and limitation fields. also updates tests and docs so everything matches what we actually support

Description

this updates the nip-11 relay info to better match the current spec. adds optional fields like banner, icon, self, terms_of_service. adds cors headers. adds limitation fields like created_at_lower_limit, created_at_upper_limit, default_limit, restricted_writes. also uses a shared constant for default limit and updates tests and docs accordingly

Related Issue

#205

Motivation and Context

this just makes nip-11 relay info match the current spec better. adds missing fields, cors headers and limitation fields so clients don’t have to guess how the relay behaves

How Has This Been Tested?

ran tests for the nip-11 changes, mainly unit tests around root request handler fields, headers and limitation mapping. also ran npm run lint and mocha tests for test/unit/handlers/request-handlers/root-request-handler.spec.ts

Screenshots (if appropriate):

Types of changes

• Non-functional change (docs, style, minor refactor)
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my code changes.
• I added a changeset, or this is docs-only and I added an empty changeset.
• All new and existing tests passed.

[coveralls]

coverage: 74.695% (+0.2%) from 74.533% — a-khushal:feat/nip11-parity into cameri:main