feature request: .prettierignore for subfolders, like .gitignore #15143

• Right now, it is not possible to place a .prettierignore file in a subfolder and have it apply to files in that subfolder, akin to how .gitignore works.
• Using --ignore-path is cumbersome to maintain, and personally I couldn't get it to work.
• Prettier config files do not have an ignorePath option to configure this there instead of in the CLI command.

It would be great if we could simply place .prettierignore files at any level deep, and for it to just work just like .gitignore does (for a given file, see get ignore files up the tree, and see if it is ignored by any of them).

Currently Prettier only uses ./.prettierignore in the working directly.