new nvim-tree.filters to point to custom files with regexes with ignore patterns

A new nvim-tree.filters that would behave exactly as nvim-tree.filters.git_ignored but we could set custom file names like .ignored.

There are some cases we don't want to git ignore some files, but we want to hide from tools like this or ripgrep, ripgrep has some extra files where you can define your ignored regex patterns like .ignore or .rgignore using
Filtering options.

Something like this:

    *nvim-tree.filters.custom_file_ignored* 
    Ignore using custom files that behave like `.gitignore`, but with a different name like `.ignored`. 
    Toggle via |nvim-tree-api.tree.toggle_custom_file_ignored_filter()|, default `G`
      Type: `{string}`, Default: `{}`

Start by reading the existing nvim-tree.filters.git_ignored behavior and the nvim-tree-api.tree.toggle_custom_file_ignored_filter() entry point. Compare the requested custom ignore filenames and regex patterns with the current filter configuration, then verify that the toggle and default G mapping behave as described.