It provides significant advantages when it comes to noticing bugs and including types (also for docs) in the code from the start. I feel that TypeScript is widely enough known at this point (and close enough to JavaScript to figure it out quickly) to not be too much of a barrier.

On the contrary, it makes it easier for people to contribute as their code is more likely to actually work.

Is the programming language really the important thing that limits who can contribute? People who are skilled in writing text editors and development tools can probably adapt to TypeScript without any issue.

TypeScript is really just JavaScript with intuitive type checking.