Expose pict-rs maximum file size in Lemmy API

[Sjmarf]

Requirements

• Is this a feature request? For questions or discussions use https://lemmy.ml/c/lemmy_support
• Did you check to see if this issue already exists?
• Is this only a feature request? Do not put multiple feature requests in one issue.
• Is this a backend issue? Use the lemmy-ui repo for UI / frontend issues.
• Do you agree to follow the rules in our Code of Conduct?

Is your proposal related to a problem?

If I upload an image that exceeds the instance's maximum file size limit, I get an error. However, there's no way (that I can tell) of knowing what the limit actually is.

Describe the solution you'd like.

Ideally, the error message would tell you the maximum file size. In addition, it would be nice if the maximum file size could be queried through the API so that a client can display a warning before attempting to upload the image.

Describe alternatives you've considered.

Additional context

No response

[Nutomic]

@asonix Does pictrs expose these config values anywhere in the API? I didnt find it in the readme.

[asonix]

The config values are not exposed, but I can add that pretty easily