feat(grammar): semicolon can be omitted for the last statement in block

[anton-trunov]

Closes #427

• I have updated CHANGELOG.md
• I have added tests to demonstrate the contribution is correctly implemented: this usually includes both positive and negative tests, showing the happy path(s) and featuring intentionally broken cases
• I have run all the tests locally and no test failure was reported
• I have run the linter, formatter and spellchecker
• I did not do unrelated and/or undiscussed refactorings

[novusnota]

Cool idea with lookaheads!

Unfortunately (?), lookahead assertions are not feasible in LR(1) grammar, which would cause a bit of pondering around to implement this in the tree-sitter :)

I'll probably go with grouping all statements requiring a terminating semicolon and approaching them similar to how it's done in #395. UPD: or just choice(";", "}"), hmm