Improve the editor HTML template
Improve the editor HTML template

- Darken the header tab background to match the default editor
  background color.
- Hide the distracting focus outlines for the editor and game canvas.
- Use a pure black background for the game canvas to better distinguish it
  from the editor and provide a more neutral background.
- Use a bold font weight for the Start Godot editor button on the
  loader page.
- Link to the web editor documentation on the loader page.
- Clarify what happens when clicking "OK" in the persistent data removal
  warning dialog.
- Tidy up the HTML template by removing obsolete attributes.

guilhermefelipecgs/godot,honix/godot,Shockblast/godot,Shockblast/godot,Shockblast/godot,honix/godot,DmitriySalnikov/godot,Shockblast/godot,firefly2442/godot,sanikoyes/godot,vkbsb/godot,josempans/godot,BastiaanOlij/godot,Valentactive/godot,DmitriySalnikov/godot,godotengine/godot,vnen/godot,BastiaanOlij/godot,vkbsb/godot,firefly2442/godot,Faless/godot,godotengine/godot,MarianoGnu/godot,vnen/godot,BastiaanOlij/godot,godotengine/godot,Zylann/godot,sanikoyes/godot,firefly2442/godot,sanikoyes/godot,sanikoyes/godot,josempans/godot,josempans/godot,DmitriySalnikov/godot,Faless/godot,DmitriySalnikov/godot,MarianoGnu/godot,pkowal1982/godot,BastiaanOlij/godot,vnen/godot,akien-mga/godot,Faless/godot,guilhermefelipecgs/godot,vkbsb/godot,pkowal1982/godot,guilhermefelipecgs/godot,sanikoyes/godot,Faless/godot,honix/godot,vnen/godot,vkbsb/godot,MarianoGnu/godot,sanikoyes/godot,pkowal1982/godot,Zylann/godot,vkbsb/godot,akien-mga/godot,Shockblast/godot,pkowal1982/godot,firefly2442/godot,Zylann/godot,guilhermefelipecgs/godot,vkbsb/godot,pkowal1982/godot,vkbsb/godot,Faless/godot,Valentactive/godot,akien-mga/godot,godotengine/godot,honix/godot,MarianoGnu/godot,firefly2442/godot,godotengine/godot,firefly2442/godot,josempans/godot,sanikoyes/godot,guilhermefelipecgs/godot,Shockblast/godot,Zylann/godot,BastiaanOlij/godot,DmitriySalnikov/godot,vnen/godot,Zylann/godot,akien-mga/godot,DmitriySalnikov/godot,Valentactive/godot,guilhermefelipecgs/godot,BastiaanOlij/godot,Faless/godot,josempans/godot,MarianoGnu/godot,firefly2442/godot,Shockblast/godot,ZuBsPaCe/godot,josempans/godot,guilhermefelipecgs/godot,vnen/godot,godotengine/godot,Valentactive/godot,MarianoGnu/godot,guilhermefelipecgs/godot,Shockblast/godot,ZuBsPaCe/godot,pkowal1982/godot,ZuBsPaCe/godot,ZuBsPaCe/godot,MarianoGnu/godot,ZuBsPaCe/godot,godotengine/godot,akien-mga/godot,josempans/godot,vnen/godot,Zylann/godot,vnen/godot,pkowal1982/godot,BastiaanOlij/godot,ZuBsPaCe/godot,Faless/godot,BastiaanOlij/godot,Zylann/godot,Valentactive/godot,ZuBsPaCe/godot,DmitriySalnikov/godot,honix/godot,Valentactive/godot,firefly2442/godot,josempans/godot,Zylann/godot,akien-mga/godot,MarianoGnu/godot,Valentactive/godot,ZuBsPaCe/godot,vkbsb/godot,sanikoyes/godot,akien-mga/godot,godotengine/godot,akien-mga/godot,honix/godot,Valentactive/godot,pkowal1982/godot,Faless/godot