feat: Update of the Book→Operators page

* All precedences match Tact 1.3.0
* Added bitwise XOR operator `^`
* Fixed minor typos and corrected some descriptions
* Added a table of operators in decreasing order of their precedences

Note, that the only link leading to Language section now has a proper link to the Reference section.
This is intentional, as the Lang->Ref rename is almost there :)

Author: novusnota