Enable selection of coding fonts with ligatures in Python, R, and Tcl editors

Fonts like Fira Code (open source) make source code more readable by representing common character combinations with unified symbols. For example, == looks like a double-wide equals, -> looks like an arrow, >= looks like a standard mathematical greater-than-or-equal symbol. I already have support for fonts like this in my JetBrains editors, but it would be nice to also have it in the PythonCreator, PythonCaller, RCaller, and TclCaller transformers, as well as the scripted user parameter editor.