[Tolk] Create a reference documentation MVP

[reveloper]

• Create independent FunC Tolk reference documentation
• Replace the differences pages with new reference documentation

[anton-trunov]

We should not replace the FunC-to-Tolk migration guides: there are still a lot of seasoned FunC programmers for whom this is really valuable info.

[reveloper]

@anton-trunov I mentioned the differences in the pages as reference documentation like https://beta-docs.ton.org/languages/tolk/from-func/in-detail (such pages will become outdated with every Tolk 1.x release).

Anyway, this is a summary of the plan discussed by @tolk-vm, I believe he'll add more details and fill in his own vision after the Tolk v1.2 release.