Investigate using typescript

[evqna]

Is your feature request related to a problem? Please describe.

Working on the recent refactoring has been frustrating as javascript offers practically no way to enforce contracts between different functions (in terms of what values they expect and return). This makes it difficult to keep the codebase in sync when changing the object layout of a return value or a parameter.

We have currently been using JSdoc as a bandaid to get some help from VSCode autocomplete but its power is limited.

Describe the solution you'd like

Using typescript in some places (not necessarily converting the whole code base) could let us define schemas for common data types and check that we do not misuse them. Possible use cases:

• Describe the schema of linter json output
• Enforce the GitHub checks report object schema as the output of the report merging code
• Enforce a common interface on all linter runner classes

An other reoccurring has been passing too few parameters to some functions that then silently fail in obscure cases.

Describe alternatives you've considered

It may be possible to write more complex JSDoc rules but these only help autocompletion, they do not generate build errors.