Apple silicon workaround

[tan-ad]

I thought it would be helpful to have the workaround to open the app on Apple Silicon computers found in this issue on the README. I would open a PR but I'm not a contributor. I wrote up a draft you could add to the README (or add me as a contributor, I'd love to help!):

### Troubleshooting for Apple Silicon (M-series Macs):
If you are on a newer M-series Mac, the app fails to open silently, or says `killed` in the terminal, macOS may be confusing the single-file executable for a broken Mac application bundle due to the `.app` extension. Furthermore, the current macOS release is built for Intel (x86_64) and requires Rosetta to run.

You can use the Terminal to fix the file extension and force it to run:
> 1. Open **Terminal** and navigate to where you extracted the file: e.g. `cd ~/Downloads`
> 2. Rename the file extension so macOS treats it as a raw executable: `mv BeatmapExporter.app BeatmapExporter.bin`
> 3. Make the file executable: `chmod +x BeatmapExporter.bin`
> 4. Run the program through Rosetta translation: `arch -x86_64 ./BeatmapExporter.bin`
> 
> *(Note: If you have never used Rosetta before, macOS may prompt you to install it when running the final command).*