docs: reformat and update CONTRIBUTING.md (#37951)
docs: reformat and update CONTRIBUTING.md (#37951)

This doc is very old and rusty. I'm reformatting it to follow the one-setence-per-line rule.
I also updated a few sections, since they were either poorly written or obsolete.

PR Close #37951

shairez/angular,gnomeontherun/angular,gdi2290/angular,ocombe/angular,manekinekko/angular,shairez/angular,gdi2290/angular,gdi2290/angular,wKoza/angular,blesh/angular,angular/angular,ocombe/angular,JiaLiPassion/angular,manekinekko/angular,IdeaBlade/angular,brandonroberts/angular,gkalpak/angular,brandonroberts/angular,brandonroberts/angular,manekinekko/angular,alxhub/angular,blesh/angular,mgechev/angular,mgechev/angular,mgechev/angular,gdi2290/angular,JiaLiPassion/angular,angular/angular,shairez/angular,JiaLiPassion/angular,angular-indonesia/angular,alxhub/angular,angular/angular,gdi2290/angular,gnomeontherun/angular,blesh/angular,ocombe/angular,brandonroberts/angular,angular/angular,IdeaBlade/angular,gnomeontherun/angular,alxhub/angular,manekinekko/angular,angular-indonesia/angular,IdeaBlade/angular,angular-indonesia/angular,gdi2290/angular,wKoza/angular,ocombe/angular,wKoza/angular,blesh/angular,wKoza/angular,IdeaBlade/angular,manekinekko/angular,shairez/angular,blesh/angular,gkalpak/angular,shairez/angular,alxhub/angular,JiaLiPassion/angular,ocombe/angular,alxhub/angular,mgechev/angular,brandonroberts/angular,gkalpak/angular,gnomeontherun/angular,angular-indonesia/angular,IdeaBlade/angular,wKoza/angular,brandonroberts/angular,mgechev/angular,manekinekko/angular,ocombe/angular,wKoza/angular,gkalpak/angular