Update batchTrans.js - Issue #11

[SinaElahimanesh]

Hello,
I solved it by adding a new function, alternativeBatchTranslation, in batchTrans.js file.
In case of error, it catches the error and by finding the error reason, translates all the words and also returns the error type.
So in case of
const texts = ["", "Hallo Welt", "guten morgen"]; google .translateBatch(texts) .then(res => console.log("batch translation: ", res));
The result will be like bellow:
[ 'ERROR: error translating batch: The input text length must be of type string between 1 and 5000 characters', 'Hello World', 'Good morning' ]
As it can be seen the first box has an error, and the second and third element is translated successfully =)

I am eagerly waiting for you to merge my pull request and accept it.
Thanks a lot.
Sina Elahimanesh