Improve the use of TypeScript types

[sehilyi]

There is room for improvement regarding the use of TypeScript types. This will enable us to maintain and improve the package in a more robust way.

• HiGlass does not provide types, so we are partly implementing them in our repo (https://github.com/gosling-lang/gosling.js/blob/master/src/missing-types.d.ts).

  • https://github.com/gosling-lang/gosling.js/issues/702

• Many any types can be removed by inferring/specifying proper types

  • https://github.com/gosling-lang/gosling.js/issues/695