Add documentation to the an_validate_lib_strings action

Author: spencertransier

lib/fastlane/plugin/wpmreleasetoolkit/actions/android/an_validate_lib_strings_action.rb

@@ -33,7 +33,19 @@ def self.return_value
       end
 
       def self.details
-        'Checks that the strings to be localised are updated from the libs into the main application file'
+        <<~DETAILS
+          Checks that the strings to be localised are updated from the libs into the main application file
+
+          For the `lib_strings_path` ConfigItem, it is an array of Hashes, each describing a library and
+          containing these specific keys:
+            - `:library`: The human readable name of the library, used to display in console messages
+            - `:strings_path`: The path to the strings.xml file of the library to merge into the main one
+            - `:exclusions`: An array of strings keys to exclude during merge. Any of those keys from the
+               library's `strings.xml` will be skipped and won't be merged into the main one.
+            - `:source_id`: An optional `String` which will be added as the `a8c-src-lib` XML attribute
+               to strings coming from this library, to help identify their source in the merged file.
+            - `:add_ignore_attr`: If set to `true`, will add `tools:ignore="UnusedResources"` to merged strings.
+        DETAILS
       end
 
       def self.available_options
@@ -44,7 +56,7 @@ def self.available_options
                                        type: String),
           FastlaneCore::ConfigItem.new(key: :libs_strings_path,
                                        env_name: 'CHECK_LIBS_STRINGS_PATH',
-                                       description: 'The list of libs to merge',
+                                       description: 'The list of libs to merge. This should be an array of Hashes.',
                                        optional: false,
                                        type: Array),
           FastlaneCore::ConfigItem.new(key: :diff_url,