Fix #118: Indicate more details about 403 forbidden

Author: Stichoza

README.md

@@ -174,7 +174,7 @@ In addition, `translate()` and `trans()` methods will return `null` if there is
  - `413 Request Entity Too Large` response:
    This error means that your input string is too long. Google only allows a maximum of 5000 characters to be translated at once. If you want to translate a longer text, you can split it to shorter parts, and translate them one-by-one.
  - `403 Forbidden` response:
-   This is not an issue with this package. Google Translate itself has some problems when it comes to translating some characters. See https://github.com/Stichoza/google-translate-php/issues/119#issuecomment-558078133
+   This is not an issue with this package. Google Translate itself has some problems when it comes to translating some characters and HTML entities. See https://github.com/Stichoza/google-translate-php/issues/119#issuecomment-558078133
 
 
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