CI and common update:

-added webpage deploymnet stage
-added separate build stage which build all binaries and generate documentation
-added Emscripten build stage for merge to master only
-added VBO batch rendering (current default, no render mode switch yet)
-fixed camera positioning calculation
-fixed buffer issue with WebGL
-added viewport scalling (at least 300 pixels height). Pixels are scalled if screen is bigger.
-center demos gameplay area
-added fullpage html template for Emscripten build

.gitignore

@@ -5,6 +5,8 @@
 !README.md
 !./dub.json
 !.gitignore
+!codecov.yml
+!skeleton.html
 !meson.build
 !meson_options.txt
 !compile_wasm.py