Update peer dependency to 5

[Tyriar]

Seeing on install now:

warning " > xterm-addon-canvas@0.2.0-beta.15" has incorrect peer dependency "xterm@^4.0.0".
warning " > xterm-addon-ligatures@0.6.0-beta.14" has incorrect peer dependency "xterm@^4.0.0".
warning " > xterm-addon-search@0.10.0-beta.3" has incorrect peer dependency "xterm@^4.0.0".
warning " > xterm-addon-unicode11@0.4.0-beta.3" has incorrect peer dependency "xterm@^4.0.0".
warning " > xterm-addon-webgl@0.13.0-beta.32" has incorrect peer dependency "xterm@^4.0.0".