Enable generating new migrations with shortcuts 'js' and 'ts'

[IvanKiral]

Motivation

Usually, when deciding between javascript and typescript, you can write shortcuts 'js' or 'ts' instead of full names 'javascript' and 'typescript'. Slight improvement, but it can reduce the annoyance of always getting errors when specifying only shortcuts.

Proposed solution

Add shortcuts into src/cmds/migration.add.ts.

Additional context

Add any other context, screenshots, or reference links about the feature request here.