Add entry from doi

Hi @msandova I've managed to add the function. But I have never used rust nor gtk, so I hope this mr is useful 😬

I've added a new tab to parse a bib entry from doi. However, I guess to bring it to production one should catch possible errors. What do you think about that?

Fixes: #43 (closed)

• parse bib from doi
• rename key to "lastnameYY"
• catch error if doi does not exist
• catch error if no internet connection