Fixed several quirks, added features

BWTC32Key can now actually read and save .B3K files rather than relying on users to make them via text editors. I also fixed some macOS compatibility quirks and made decoding from places like Discord and Twitter posts more straightforward, and in the process of making read and write of B3K files possible I also made it possible for larger files to be done because of my introduction of B3K file generation and reading, which means that you don’t have to touch the input and output boxes. After encoding, you can download THAT output box as a B3K, and when decoding a B3K file, you can upload it to the relevant field, and it will be read into the decode box rather than needing a text editor.