Enables struct fields punning, i.e. Foo {foo, bar} is syntactic sugar for Foo { foo: foo, bar: bar }

[vitorpy]

Closes #253

• I have updated CHANGELOG.md
• I have added unit tests to demonstrate the contribution is correctly implemented
• I have run all the tests locally and no test failure was reported
• I did not do unrelated and/or undiscussed refactorings

[anton-trunov]

Looks like you go in the right direction. I'd like to have a couple more tests here that are not just grammar tests:

• one runtime test should go into /~https://github.com/tact-lang/tact/blob/main/src/test/features/ordering.tact with the corresponding test in /~https://github.com/tact-lang/tact/blob/main/src/test/feature-ordering.spec.ts (this essentially tests structures, can be renamed to feature-struct actually)
• a failing test for the typechecker when there is no identifier with the same name as a struct field: /~https://github.com/tact-lang/tact/tree/main/src/types/test-failed

[vitorpy]

Will fix conflicts.

[vitorpy]

Changelog changes don´t look right, looking.

[anton-trunov]

@vitorpy Thanks a lot for contributing yet another nice feature!