Add a dynamic ISA reference

[raccog]

Draft branch for #297.

Here's my plan on how to implement this feature:

• [x] Static sliderules tab UI with instruction encodings for 2 instructions
• [x] Tooltip UI for 2 instructions at a single location
• [ ] Tooltip UI for 2 instructions at multiple locations
• [ ] Dynamic sliderules tab UI with instruction encodings for 2 instructions per instruction type
• [ ] Dynamic tooltip UI with instruction encodings for 2 instructions per instruction type
• [ ] Fill out instruction details so that all instructions are included in the UI

Added a new tab for an ISA reference table.

[raccog]

Here's a demo of a tooltip that can show up when hovering over instructions in the VSRTL window. The tooltip shows the binary encoding of an add instruction.

[raccog]

Replacing this draft with #329.