We could use similar comments for imports related to other `@types` packages,
but the need to do it for `@types/embark` (located in
`packages/embark-typings`) seems more pressing since `import ... from "embark"`
statements in the monorepo can be so easily misunderstood.
Note that the comments, and indeed the whole lines, are automatically erased
during babel transpilation of TypeScript since TS types aren't relevant after
the `.js` files are built.
If a package uses only `.js` then supply `--extensions ".js"`. If a package
uses only `.ts` then supply `--extensions ".ts"`. If a package uses both, then
supply `--extensions ".js,.ts"`.
The reason for this is that adding/removing TS/JS support ought to occasion
revising a package's `package.json` file and adjusting other scripts as well,
e.g. for linting. With these changes, it won't work to simply start adding
`.ts` files in a package's `src/` directory, which should prompt the developer
to review `package.json` and make the appropriate changes, and/or other
developers may realize changes need to be made during code review.