Feature request: Add CLI flag to specify opcode variant

[pushfoo]

Running a source file containing SCHIP or XO-CHIP instructions (ie hires) with -r / --run appears to only partially work.

For example, hires assembles correctly to 00FF, but the instruction is interpreted in CHIP-8 mode and produces an invalid opcode error.

It would be easier to allow manually specifying the opcode variant as a CLI flag than to try to write auto-detect logic.

[pushfoo]

This was already added, just further down in the docs than expected.

It may be a good idea to move the presets section above the quirks section in the README to make this more obvious for other users.

[gulrak]

Yeah, the readme is not that well organized, I'll see what I can do. Thanks for the comment.

[pushfoo]

Are you open to contributors using markdown tables and splitting the README into multiple documents? I don't know what the best practices for documenting C++ projects are considered to be, so I'd appreciate your input on that before jumping in.