Add a HardLimiter effect to the default bus layout

[mieldepoche]

Reading the docs:

Adding a limiter to the final point of the Master bus is good practice, as it offers an easy safeguard against clipping.

Why not have one by default then?

pros:

• safe default for beginner users and jam games

cons:

• users who don't want it have to delete it manually

I am not knowledgeable when it comes to audio stuff, but wouldn't that be a sensible default?

[Mickeon]

This reminds me of when I explicitly mentioned to reduce how important it sounded in the class reference:

Well, I wouldn't say "always". If that's true the default bus layout generated with a project would come with it. Otherwise, it'd be boilerplate to set up all the time. Different projects for different purposes...

In the manual the filter was documented by @skyace65 in godotengine/godot-docs#9401 , but this is at the end of the day the same description as the prior filter.