When shortcut modifiers (modifier keys such as CTRL, which do not participate in
composing character input) are pressed, we try to suppress the keypress
event, as browsers do not reliably generate it. This means that
subsequent key events are decoded only based on the keydown event.

Due to a type error (comparing a string to a number), shift was
mistakenly treated as a shortcut modifier, preventing text input which
relied on shift, such as _ and %, from being generated.

Keyboard Handling [8/8]: Introduce substituteCodepoint() to replace code points which don't have a keysym with ones that do

For now, the only code points this is done for are {s, S, t, T} with comma below (used in Romanian),
 which are replaced by {s, S, t, T} Cedilla.

Relies on the libraries chai and mocha (available via npm from Node.JS).

Add anything installed via npm to the .gitignore file.