Try to resolve knexfile.ts when knexfile.js does not exist

[kibertoad]

fixes #3003

[kibertoad]

@eioo @dgadelha Please take a look if it addressed the problem that you are having.

[dgadelha]

It parses knexfile.ts, but generated migrations are generated as js files, which is a different behavior from what was at 0.15 (it generated ts migration files if your knexfile was ts)

Also, thanks for the quick fix

[kibertoad]

Hmmm, interesting. Why not just pass extension that you want though? I'll see what I can do to get old behavior back.

[dgadelha]

It's just to keep the standards for a project, if you're using a TypeScript knexfile, you'll probably want TypeScript migrations too, plus restores the behavior that 0.16 broke.

[kibertoad]

@dgadelha That's a separate low-impact issue, though, that is easily solved with minimum amount of changes from the user side. Since that would require reshuffling code around quite a bit, I'll address it in a separate PR.