* common: move iterator functionality into separate IteratorModule
* wasm: allow internal lib dependencies and iterator
* wasm: added functions for layers revising
This patch adds functions to thorvgwasm.cpp:
layers() - that return a list of paints in a picture
bounds() - that returns a bounds of a given paint
setOpacity() - that sets the opacity of a given paint
This patch adds the mimetype parameter for load() function and adds storing of
an original size after successful loading. Added function originalSize().
This patch adds saveTvg() function into thorvgwasm.cpp.
Functions saves tvg using File System API.
To enable fs, changed build flag: -s FORCE_FILESYSTEM=1.
Increase in result thorvg-wasm.js size: about 68kB to about 125kB.
If viewer calls load() with a data which does not have size changes of both
viewbox and canvas, then load() does not set a scale value.
This makes incorrect result on viewer side.
So thorvg wasm should set a scale value, whenever load() is called.
