Doc clarity/detail for extra spacing properties
Doc clarity/detail for extra spacing properties

Re: Space spacing being in addition to character spacing see:

 * <https://github.com/godotengine/godot/blob/d7b85fbaa1fc438effe406c9d7f973749eb4e527/scene/resources/dynamic_font.cpp#L858-L859>

Re: Value being able to be negative see example here:

 * <https://github.com/godotengine/godot/issues/38630>

But also note that nodes other than `Label` may not currently render extra space spacing correctly.

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