Splitter property for initial size should be called panelSize on the showcase

[daniel-lang]

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Plunkr Case (Bug Reports)
Please demonstrate your case at stackblitz by using the issue template below. Issues without a test case have much less possibility to be reviewd in detail and assisted.

https://stackblitz.com/github/primefaces/primeng-issue-template

Current behavior
The showcase calls the property to set the initial size of the panels in the splitter component size at some places, panelSize at others. Looking at the source code, the correct name should be panelSize.
When using size, angular complains, since it isn't a known property of p-splitter.

Expected behavior
Correct documentation/showcase and no error.

Minimal reproduction of the problem with instructions

• visit https://primefaces.org/primeng/showcase/#/splitter
• checkout the example of Initial Sizes or the table of properties.

What is the motivation / use case for changing the behavior?
Correct the documentation. Help people not have angular errors when using the wrong property.

Please tell us about your environment:

• Angular version: 11.0.6

• PrimeNG version: 11.1.0

• Browser: all

• Language:

• Node (for AoT issues): node --version = 15.2.1