Request: mention in docs what to choose for each ad-network for inline-adaptive-banner ads

[Liran Barsisa]

Admob support a flexible size of a banner ad, called "inline-adaptive-banner" ad:
https://developers.google.com/admob/android/banner/inline-adaptive

However, it's not mentioned on the docs of various ad-networks, that we can use them, and doesn't mention what to choose for the ad-network for them, either.

For example, for Liftoff/Vungle, it's mentioned in the changelog that:
"Updated the adapter to support inline adaptive banner requests."

https://developers.google.com/admob/android/mediation/liftoff-monetize#version-6.7.0.0

However, there is no mention there anywhere what to choose for it. No instructions.

Instead we actually have "Banner" and a weird item called "300x250 Banner". 
https://developers.google.com/admob/android/mediation/liftoff-monetize#add_new_placements

On Vungle/Liftoff website, it also doesn't mention inline-adaptive-banner. Instead they have "MREC", "Banner", and "In Line".

Please update the docs of each ad-source about this type of ad support, and also update the table of all ad-networks, here:
https://developers.google.com/admob/android/choose-networks

Currently we only see there "banner", which is misleading as it might not include this type of banner ad for some of them.

Also requested here:
https://github.com/googleads/googleads-mobile-android-mediation/issues/556