Support for UTF Supplementary Private Use Area-A

[EndlessDelirium]

MaterialDesignIcons seems to have moved their icons from the Private Use Area (U+E000..U+F8FF) to the Supplementary Private Use Area-A (U+F0000..U+FFFFD).
Iconize internally uses a lookup table where type "char" is used to store the unicode character. This unfortunately doesn't work for "Supplementary Private Use Area-A" as it requires either UTF-16 surrogate pairs or UTF-32.
Easiest fix is likely to simply use "string" instead of "char" for storing the unicode character of the icon.

[gercobrandwijk]

As you mentioned in #178 you converted the font so that it uses the PUA blocks, so that it can be used in this library without the need for changing char to string. How can I convert the latest font of material design icons (v5.8.55) by myself, like you did for version 5.1.45?

[EndlessDelirium]

This can be done fairly easily with FontForge (https://fontforge.org/):

1. Edit>Select>Glyphs worth outputting
2. Cut selection
3. View>GoTo to navigate to Private Use Area-A
4. Paste