WASM support

[blaind]

WASM is not currently supported. Investigate solutions to build for it.

[blaind]

Error message:

$ cargo build --target wasm32-unknown-unknown
[...]
   Compiling ttf2mesh-sys v0.1.2 (/ttf2mesh-rs/ttf2mesh-sys)
The following warnings were emitted during compilation:

warning: ttf2mesh/ttf2mesh.c:42:13: fatal error: 'dirent.h' file not found
warning: #   include <dirent.h>
warning:             ^~~~~~~~~~
warning: 1 error generated.

The root cause is, that ttf2mesh-sys needs to build the ttf2mesh.c as an intermediate target to be linked into the final wasm binary by rust. Not sure, what would be the best way to do it.

One (possible?) option is to use emscripten, after installing it and:

CC=emcc cargo build --target wasm32-unknown-unknown

This goes a step further, but results into multiple errors of sys::ttf_ missing, e.g.

error[E0425]: cannot find function `ttf_glyph2mesh3d` in crate `sys`
  --> src/glyph.rs:64:18
   |
64 |             sys::ttf_glyph2mesh3d(
   |                  ^^^^^^^^^^^^^^^^ not found in `sys`

these are exposed by ttf2mesh-sys/ttf2mesh/ttf2mesh.h, and bindings generated by bindgen at ttf2mesh-sys/build.rs