Adds jsFunctionKey to jsObjectKey

As per a user's feature request, this adds a slightly higher specificity
for object keys that define a function.
Removing `-` as a valid character for jsObjectKey
Better whitespace support for jsFunctionKey

This allows 0 or more spaces after the `:` character in a jsFunctionKey
Merge pull request #127 from pangloss/feature/add-jsfunctionkey

Adds jsFunctionKey highlight group

jsFunctionKey is used to target object keys that have functions as a value
Fixes jsObjectKey, removes dashes in Identifiers