downlevel interface and object get/set accessors in <4.3

[nbilyk]

Interface and object literal getters/setters were introduced in TS 4.3

Support downleveling these to properties like is done in class definitions.

https://www.typescriptlang.org/docs/handbook/release-notes/typescript-4-3.html

[nbilyk]

I'm willing to submit a PR for this but I have some PRs incoming first for general improvements before I work through my 5.3 -> 3.7 issues.

[nbilyk]

I am just noticing that this repo has gone into KTLO and hasn't had a commit in 2 years. Unless I see activity I will iterate within my fork and just post a link to the community. This library is one of a kind and I'd like to see it revived.