Add file bundling to elf to uf2 conversion

[mattnite]

Implement file containers for uf2. There's already a build option for the user to select whether the source files should be bundled, which ends up hitting a panic if it's set to true right now. If you parse DWARF info, you'll be able to assemble a list of all used files, and then add them to the uf2 file using the addFile() function.

[pqcfox]

Would love to help contribute this feature! Is this available to work on?

[mattnite]

@foxmoder Yes it is! here is the relevant code path. Let me know if you need any other guidance!