FIX - GetAppDomains readme (#230)

This pull request updates the documentation for the `getAppDomain`
method in the `README.md` file to clarify the meaning of the `domain`
property.

Documentation improvement:

* Updated the description of the `domain` property to specify that it
refers to the domain used for handling deeplinks, rather than just the
environment the app is pointing to.

---------

Co-authored-by: Jesus Prieto <[email protected]>

Author: alexanegon

README.md

@@ -817,7 +817,8 @@ Return info about appDomain
 getAppDomain: () => Promise<{domain: string}>;
 ```
 
-`domain`: the domain value of the environment that the app is pointing to.
+`domain`: the domain value of the environment that the app uses for handling
+deeplinks.
 
 ### getAppMetadata