docs: fix style guide example app included as routing (#45148)
docs: fix style guide example app included as routing (#45148)

in the aio example apps page the style guide for documentation
contributions is included in the Routing section instead of being
in its own section, add a documentation section and include the example
in that one

PR Close #45148

gkalpak/angular,angular/angular,gnomeontherun/angular,gkalpak/angular,angular/angular,angular-indonesia/angular,angular-indonesia/angular,JiaLiPassion/angular,gnomeontherun/angular,angular-indonesia/angular,gnomeontherun/angular,angular/angular,JiaLiPassion/angular,angular/angular,JiaLiPassion/angular,angular-indonesia/angular,gkalpak/angular,gkalpak/angular,gnomeontherun/angular,JiaLiPassion/angular