Expose font size parameter when using web-client

[alphajoza]

web-client is a remarkable feature. Some parameters such as font and theme can already be configured. It would be really nice if we set the font size too.

Note:
this can be done via adding fontSize to Terminal object defined in:
zellij/zellij-client/assets/terminal.js

[imsnif]

Totally agree - as a workaround though you can do Ctrl + or Ctrl - to increase/decrease the font size at runtime.