Adds notes on annotating type parameters.
Adds notes on annotating type parameters.

It may not be obvious how to get rid of "second-level" platform types.
Also, not all annotations from the list work in the same way.

Judging my [confusion and the amount of tinkering necessary](https://stackoverflow.com/q/49646581/539599), it's worth documenting this here.

Maybe we should try out more types of annotations to find out which can be used on types?
hltj/kotlin-web-site-cn,JetBrains/kotlin-web-site,JetBrains/kotlin-web-site,hltj/kotlin-web-site-cn,JetBrains/kotlin-web-site,meilalina/kotlin-web-site,meilalina/kotlin-web-site,JetBrains/kotlin-web-site,hltj/kotlin-web-site-cn,hltj/kotlin-web-site-cn,JetBrains/kotlin-web-site,JetBrains/kotlin-web-site,meilalina/kotlin-web-site,hltj/kotlin-web-site-cn,meilalina/kotlin-web-site,hltj/kotlin-web-site-cn