docs: add empty support channel section to help page

[goffxnca]

PR updates the /help page w/ 3 main parts:

• Main Support Channels: Added key channels like Telegram (Near Dev), Discord, Zulip, X, and Dev Hub.
• Telegram Folder (21 chats): Grouped 21 NEAR-related TG chats into 1 table w/ a folder link.
• NearBuilders Groups (15 chats): Picked 15 unique groups from the 31 on nearbuilders.com. where 14 were already in the TG folder and 2 were dropped:
  https://t.me/near_sdk_js: links to a no longer exists personal acct.
  https://t.me/+lf7vb2MAEgdjOGQx: bio links to a sus/external group, now expired.

Live preview: New Help Page.
Fixes #2328

[goffxnca]

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