feat: Add mjs options to prettier

[alexrecuenco]

See here: https://prettier.io/docs/en/configuration.html

Now ESM modules are allowed for prettier config files

At the same time, it might make sense to use prettier.resolveConfig, which returns null if no config is found. That way you don't need to keep matching prettier's interface ad-infinitum

Changes

Prettier allows mjs files.

Context

Prettier now allows ESM configuration

Documentation (please check one with an [x])

• I have updated the documentation, or
• No documentation update is required

How I've tested my work (please select one)

I have verified these changes via:

• Code inspection only, or
• Newly added/modified unit tests, or
• No unit tests but ran on a real repository, or
• Both unit tests + ran on a real repository

[viceice]

can you propose a PR to use the resolve config function?

[alexrecuenco]

I am not sure I get what "Snapshots have been added in this PR. Use toMatch instead." means

[alexrecuenco]

can you propose a PR to use the resolve config function?

If I have enough time, I'll try, I am unfortunately quite busy lately

[rarkins]

Doesn't prettier.resolveConfig also execute any JS found? Ie a massive attack vector if renovate were to allow users to execute arbitrary code?

[alexrecuenco]

Doesn't prettier.resolveConfig also execute any JS found? Ie a massive attack vector if renovate were to allow users to execute arbitrary code?

If you know that to be the case, then ignore the suggestion, thanks for your time