Add Greek translation

[swaranan]

Have been using this library for long.. But it does not working for Greek language. Have tried with both "el" & "gr". But it does not recognise the language.

[monovertex]

That is because we're currently missing the Greek translation. You are welcome to open a PR to add it, take a look here for an example: #503

[ilaydaozdemir99]

I have added the Greek (gr) language, please check the active PR.

[swaranan]

Thanks, :)