Draft SMFL-based native canvas implementation

[mmore500]

This pull request aims to add a native backend for emp::web::Canvas so that we can draw to a canvas and save results as an image file from our natively-compiled applications. The idea is to provide two emp::web::Canvas classes (one in web/_NativeCanvas.hpp and one in web/_EmscriptenCanvas.hpp) and then use the preprocessor __EMSCRIPTEN__ to switch out which class is used. For the native implementation, we ape only the drawing and safe-to-file methods... not the full dom model or any of Canvas's "Widget"-related attributes.

Under the hood, this PR uses the "Simple and Fast Multimedia Library" https://www.sfml-dev.org/

pro:

• cross-platform (Windows, Linux, macOS and soon Android & iOS)
• looks like it will continue to exist well into the future: under active development (last commit yesterday https://github.com/SFML/SFML/) & 13-year development history
• low barrier to entry: binaries available through apt and homebrew (macos) package managers, can link with just -lsfml-graphics flag
• was recommended in the reddit posts I was trawling through 🤷

con:

• NOT header-only

I've got some minimal working code put together (see image!), but lots left unimplemented. If we decide to move in this direction, this might make for a good undergraduate project!

[codecov]

Codecov Report

Merging #406 (f8e75b6) into master (d5aac4e) will increase coverage by 0.20%.
The diff coverage is 82.84%.

❗ Current head f8e75b6 differs from pull request most recent head 72eb305. Consider uploading reports for the commit 72eb305 to get more accurate results

@@            Coverage Diff             @@
##           master     #406      +/-   ##
==========================================
+ Coverage   82.78%   82.99%   +0.20%     
==========================================
  Files         298      299       +1     
  Lines       36943    34044    -2899     
==========================================
- Hits        30584    28255    -2329     
+ Misses       6359     5789     -570     

Impacted Files	Coverage Δ
include/emp/Evolve/OEE.hpp	0.00% <0.00%> (ø)
include/emp/Evolve/StateGrid.hpp	0.00% <0.00%> (ø)
include/emp/base/errors.hpp	80.00% <0.00%> (ø)
include/emp/compiler/NFA.hpp	100.00% <ø> (ø)
include/emp/compiler/RegEx.hpp	76.02% <0.00%> (ø)
include/emp/config/ConfigManager.hpp	0.00% <ø> (ø)
include/emp/config/SettingCombos.hpp	0.00% <ø> (ø)
include/emp/config/SettingConfig.hpp	0.00% <ø> (ø)
include/emp/control/ActionManager.hpp	9.09% <0.00%> (ø)
include/emp/control/SignalManager.hpp	34.48% <0.00%> (ø)
... and 163 more

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[mmore500]

Right now, this PR is structured to directly emulate emp::web::Canvas but this doesn't make a whole lot of sense because it's not a web thing.

We could put it in a new namespace like emp::sfml::Canvas .

If we did that, we could potentially make a design based around a EMP_SOMETHING macro (name ideas for this?) where you would use it in your code like emp::EMP_SOMETHING::Canvas

and EMP_SOMETHING macro would resolve to web when compiling with emscripten and sfml when not

the downside being the EMP_SOMETHING macro would be kind of an ugly namespace qualifier 🤷

[mmore500]

TODO: switch from sfml to https://github.com/a-e-k/canvas_ity