* Allow users to configure phone numbers with the Khoj server
* Integration of API endpoint for updating phone number
* Add phone number association and OTP via Twilio for users connecting to WhatsApp
- When verified, store the result as such in the KhojUser object
* Add a Whatsapp.svg for configuring phone number
* Change setup hint depending on whether the user has a number already connected or not
* Add an integrity check for the intl tel js dependency
* Customize the UI based on whether the user has verified their phone number
- Update API routes to make nomenclature for phone addition and verification more straightforward (just /config/phone, etc).
- If user has not verified, prompt them for another verification code (if verification is enabled) in the configuration page
* Use the verified filter only if the user is linked to an account with an email
* Add some basic documentation for using the WhatsApp client with Khoj
* Point help text to the docs, rather than landing page info
* Update messages on various callbacks and add link to docs page to learn more about the integration
- Make the docs overview page available at docs.khoj.dev root instead of
under docs.khoj.dev/docs path
- Remove the new landing page, it is unnecessary.
- Remove /docs path prefix from links to internal doc pages
- Remove .md path suffix in internal doc pages for consistency
