Better assembly highlighting

[TheKnorx]

• gdbgui/src/js/SourceCode.tsx: Added logic for detecting assembly mnemonics and operands (like registers, memory addresses and constats)
• gdbgui/static/css/gdbgui.css: Added necessary css-style classes for highlighting the detected assembly

Summary of changes

• Gdbgui now highlights all parts of an assembly instruction, instead of interpreting it as one big instruction.
• Highlighting now looks like real gdb disassembly

Test plan

Tested by running the following commands inside the cloned repo after the changes:

cd gdbgui      # cd into source folder
npm install
npm run build
cd ..          # cd back to repo
python3 -m gdbgui