Allow Specifying File Extensions with --insert-css-requires Option in Linaria's CLI

## Describe the enhancement

I'm mainly using the CLI as I cannot fully understand and use various build environments. In the CLI options mentioned in [Linaria's CLI documentation](https://github.com/callstack/linaria/blob/master/docs/CLI.md#options), it would be even better if we could specify file extensions in addition to directory configurations when using the `--insert-css-requires` option.

## Motivation

It's useful to apply not only to `.js` files but also `.cjs`, `.mjs`, etc., especially when developing libraries or in various environments. I guess the relevant part is around here:
[https://github.com/callstack/linaria/blob/e29a54e417b6f3665320cb4d4d1c82be4c6dbafa/packages/cli/src/linaria.ts#L99](https://github.com/callstack/linaria/blob/e29a54e417b6f3665320cb4d4d1c82be4c6dbafa/packages/cli/src/linaria.ts#L99)