Allow custom query #358

Summary 💡

Allow configuring a custom query so that screen.get... can be changed.

For that, I would create two new fields in the settings panel:
selector object with the default value screen
query prefix with the default value get

Examples 🌈

If the user can change the value to for example query prefix = getAll, then the testing-playground shows the query as screen.getAllBy...

If the user can change the value to for example selector object = await page, then the testing-playground shows the query as await page.getBy...

Motivation 🔦

Now with playwright using the testing-library queries, I need to rewrite the screen.getBy... to await page.getBy. I would like to automatize this task so that I need only to copy paste what test-playground gives me.
Also, when I know that I have many components using Jest, I need to rewrite screen.getBy... to screen.getAllBy...

If you like this proposal, I can submit a PR for that