fix(filepicker_ls): use case insensitive matching for file exts

[doZennn]

• [x] I have tested this code on a steam deck or on a PC
• [x] My changes generate no new errors/warnings
• [x] This is a bugfix/hotfix
• [ ] This is a new feature

Description

Adds case insensitive matching to fix files not showing when using validFileExtensions in openFilePickerV2() . Example:

<FilePicker
    validFileExtensions={['.png']} // this would match ".png" but not ".PNG"
/>

[RodoMa92]

Nice catch @doZennn, looks good to me.