feat: Arm support

[WillLillis]

Adds autocomplete and hover capabilities for the ARM architecture.

Sources ARM's exploration tools for instruction information, and a few misc. website for the register info. I've been as thorough as (reasonably) possible in verifying the results of parsing the opcode documentation. However, given the sheer column of information, I'm sure there's a few mistakes/mistranslations hiding in there. Any and all bug reports, suggestions for improvement, etc. are more than welcome.

This will break people's existing .asm-lsp.toml files with the new arm instruction set configuration option, so publishing will require a minor version bump to 0.8.0.

The diff for this PR is quite large, but the vast majority is just the ARM opcode xml files. Regarding actual changes, we have:

• Updates to README.md, listing more documentation sources, as well as updating the examples .asm-lsp.toml config file.
• Updates to the documentation parser, allowing for parsing of the ARM documentation files (split over many files rather than one large file as in x86/x86-64, z80, etc.)
• additions to the Instruction type to store the ARM documentation's assembly templates and alias forms
• Updates to the src/lsp.rs logic to support ARM
• Corresponding tests for the new architecture

cc @bergercookie

Checks off a stretch goal in #80
Closes #17