tweak the current structural directives guide (currently mainly targeted
at the creation of custom structural directives) so that is more generic
and a point of reference for structural directives in general
this also includes the re-addition of the one-per-element section
removed in PR #40015resolves#44786
PR Close#44895
This commit adds support for generating pages that document
special Angular elements, such as `ng-content` and `ng-template`,
which have special behavior in Angular but are not directives nor
components.
Resolves#41273
PR Close#41299
dario-piotrowicz