feat: Add 'Getting Started with FORRT' page (fixes #481)

[saikumarvasa100-hash]

Description

This PR adds a new "Getting Started with FORRT" page as requested in #481.

The page includes:

• Slack Channels Overview - A table listing key Slack channels and their purposes
• Organisational Structure & Projects - Description of FORRT teams and links to current projects
• Paper-Writing Guidelines - Steps for getting involved with FORRT publications and writing standards
• Next Steps - Action items for new members

The content is designed to be concise and visually inviting, with tables, lists, and clear headings.

Fixes #481

Type of Change

• New feature (non-breaking change which adds functionality)
• Documentation/Contents/grammar update

Checklist

• I have read the CONTRIBUTING document
• My changes generate no new warnings
• I have linked the relevant issue in the PR description

[LukasWallrich]

✅ Staging Deployment Status

This PR has been successfully deployed to staging as part of an aggregated deployment.

Deployed at: 2025-12-06 00:29:23 UTC
Staging URL: https://staging.forrt.org

The staging site shows the combined state of all compatible open PRs.

[richarddushime]

@LukasWallrich @flavioazevedo would you give feedback on this ?

Thanks @saikumarvasa100-hash

a question : did you edit directly from the fork repository ?

[saikumarvasa100-hash]

Yes I had forked the repo and made changes