Migrate to NPM, Update XTerm Packages

[crutchcorn]

This PR:

• Migrates away from Yarn in favor of NPM per convos with @Tyriar
• Updates the deps of xterm -> @xterm/xterm namespacing issues for the website
• Updates TypeDoc to the lowest supported version required for the Gulp addon to not throw a legacy peer dep warning with new NPM
• Adds a temporary tsconfig item to the TypeDoc configuration to sidestep build errors with TS>5
• Regenerates docs to the new codebase of XTerm and TypeDoc