Version 5.1.0

Merge branch 'main' of https://github.com/Shin-NiL/Godot-Android-Admo…

…b-Plugin into main

Merge branch 'main' of https://github.com/Shin-NiL/Godot-Android-Admo…

…b-Plugin into main

Merge branch 'main' of https://github.com/Shin-NiL/Godot-Android-Admo…

…b-Plugin into main

Added showcase file

Closes Shin-NiL#33. Some code cleanup

Merge branch 'master' of https://github.com/Shin-NiL/Godot-Android-Ad…

…mob-Plugin

Merge branch 'master' of https://github.com/Shin-NiL/Godot-Android-Ad…

…mob-Plugin

Fixes Shin-NiL#14

Added methods to check if interstitial and rewarded ads are loaded