docs: improve API reference format

[davidlj95]

There are several spots for improvement in there. Seems those can't be easily fixed because API Documenter from API Extractor project doesn't support configuring those yet. Here they are:

• @defaultValue syntax, despite support is claimed in docs, it doesn't appear in docs if using it. So avoiding it for now. As it's an important piece of information to display.
• Title of the page isn't right:
  • Package name is Ngx meta. Should be ngx-meta
  • Property is lowercase'd
  • See https://ngx-meta.dev/api/ngx-meta.providengxmetacore/

Both could be maybe contributed to the project's repository so all users of it can benefit