Add an option to use appendCodepoints

[myrandor]

Add an option like used in svgicons2svgfont to automatically take the codepoint from the filename like this:

• Use the prefix of the file delimited by dash "-" as the codepoint to use in the font
• Remove that codepoint (and dash) from the name of the glyph/CSS.

Example:
A file named uE106-closed.svg will use "E106" as codepoint, and "closed" as glyph name and class name.