Set trailingcomma's to ES5

[ramonakira]

Since prettier changed their default setting to all instead of es5, we have to specify es5 now.

See: https://prettier.io/docs/en/options.html#trailing-commas

[jaap3]

This happened a while ago, and some projects have already been updated using this setting i.e.: https://github.com/leukeleu/at-frontend/commit/0c889a5535abaedd239eabea23e7c7ebf7794f2f

Browser support for trailing commas everywhere seems to be generally available since ~2017 (https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Trailing_commas#browser_compatibility).

I'm going with a -1 on this (just run prettier on projects to autofix the formatting)

[ramonakira]

We actually went through this before, where I proposed setting it to ES5 and at the time the rule was removed from our config because it was the default. See: #36 and now it comes back to bite us in the ass 😛

[jaap3]

I see, however that change only made it to version 1.4 (https://github.com/leukeleu/prettier-config/releases/tag/v1.4.0). Before that, the config specified "all" and after that prettier was updated to default to "all".

[ghost]

Is going with all really going to give us trouble? I like trailing commas 😄

[jaap3]

I think we should just keep "all", it's been the default for this config in all versions except one. So changing it now does more harm than good imho.