* feat: golang map types unioned with possible 'null'

Golang `map[<key>]<value>` can be `null` in json. This change unions
the Record type with `null`.
To revert to the previous behavior, use the mutation 'NotNullMaps'

* feat: use first class typescript enums

Enums are handled as first class types in Typescript. The previous behavior was seen as a more direct comparison of types, since Golang does not have native Enum support.

The previous behavior however was lossy, as it lost the enum member names. This new change is lossless, and the types can be reverted to the prior state.

The original name was too narrowly scoped.

* feat: support non-legal identifiers in field property names

Quoted string literals are allowed to be field property names. This
supports non-legal identifiers. Things like hyphenated field names.

Bumps [golang.org/x/tools](https://github.com/golang/tools) from 0.30.0 to 0.33.0.
- [Release notes](https://github.com/golang/tools/releases)
- [Commits](golang/tools@v0.30.0...v0.33.0)

---
updated-dependencies:
- dependency-name: golang.org/x/tools
  dependency-version: 0.33.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Bumps [golang.org/x/tools](https://github.com/golang/tools) from 0.33.0 to 0.34.0.
- [Release notes](https://github.com/golang/tools/releases)
- [Commits](golang/tools@v0.33.0...v0.34.0)

---
updated-dependencies:
- dependency-name: golang.org/x/tools
  dependency-version: 0.34.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

* fix: handle consts with references to external types

Consts to external types look like enums, but fail to generate.

* add comment