* add file interface that uses SDL file io to access filesystem
this fixes android not properly accessing asset system through SDL, as the default file interface uses the standard C api, which on android is directed to the apps data directory.
* remove debug logs, run clang format
* begin work on integration
* draw null tex when tex handle is null, switch to immediates for geometry translation
* fix window resizing and texture loads, switch to dynamic ubo
* remove immediate usage
* Add initial rmlui public API
* Use proper dimensions; fix texture resolution
* Remove unnecessary SetDimensions
* Cleanup & add clip mask support
* Implement blur and shadow filters
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Co-authored-by: Luke Street <luke@street.dev>