Documentation splashscreen

# Feature Request

## Motivation

We should make the documentation for the splashscreen easier to find and understand. Some people approached me and asked for help because getting the splashscreens right can be hard.

## Status quo

- The splashscreen feature for Android and iOS have been moved to the platforms.
- We have a quite good [page for splashscreens](https://cordova.apache.org/docs/en/11.x/core/features/splashscreen/index.html) but it's oddly placed in the menu at `Refrence -> Core Features -> Splashscreen`. I think it should be right the the next to the icons in **Create Apps**
- We still show the old plugin doc if you click on: Plugins -> Splashscreen : https://cordova.apache.org/docs/en/11.x/reference/cordova-plugin-splashscreen/index.html
- Some information is only buried in the PR: https://github.com/apache/cordova-android/pull/1441

## Room for improvement

I will talk to some people and try to make a few small changes that improve this. Feel free to help here:

- [ ] Move docs page in menu and make it easier to find
- [ ] Check page content and add information if necessary
- [ ] Test instructions
- [ ] Link to example SVG for splashscreen from our template

**Any further ideas?**

Start with the linked splashscreen documentation page and inspect its current menu location, then compare it with the old cordova-plugin-splashscreen page and the linked cordova-android PR. Done means the page is easier to find, its content and test instructions cover the current Android and iOS behavior, and the requested template SVG example is linked if available.

Written by the indexing model from the issue text.