Attempt to load_system_fonts() when loading SVGs

[ripytide]

The default usvg::Options skips text elements. This is because it doesn't attempt to load_system_fonts().

This PR may fix #870

[hecrj]

Is there any overhead from calling load_system_fonts?

may fix #870

Could we get some confirmation?

Also, a cargo fmt is needed!

[ripytide]

Is there any overhead from calling load_system_fonts?

According to the docs it looks in a few predefined system directories to look for available fonts. Not sure if that is classed as too much overhead.

Could we get some confirmation?

It fixed text rendering on my machine. I didn't get time to check using the code given in #870

Closing since you updated the resvg version to 0.29 and the load_system_fonts() function no longer exists, or at least it has been moved according to https://github.com/RazrFalcon/resvg/blob/master/CHANGELOG.md#removed-1