Add min/max file size limits by mime type.

[willvincent]

Closes issue #3.

Adds optional mimeMinFileSizes and mimeMaxFileSizes config options, these should work in conjunction with existing min/max and max total limits, and allow for setting min or max limits by explicit mime type or mime type wildcard group:

ie:

<script>
        // Register the plugin with FilePond
        FilePond.registerPlugin(FilePondPluginFileValidateSize);

        // Get a reference to the file input element
        const inputElement = document.querySelector('input[type="file"]');

        // Create the FilePond instance
        const pond = FilePond.create(inputElement, {
            mimeMaxFileSizes: {
                'image/*': '3MB',
                'image/gif': '5MB',
                'video/mp4': '100MB'
            }
        });
</script>

That config will allow images of any type up to 3mb, but allow gifs to be up to 5mb, and restrict mp4 videos to 100MB.

[rikschennink]

Appreciate the PR, will consider for v5