Add Hindi DN and Serbian MN

I have now added the entire DN in Hindi, as well as over 80 MN sutta in Serbian.

The Hindi texts are particularly significant, as they constitute the first time that this text has been published in a digital form. The translation is by the legendary India monk/author/genius Rahul Sankrityayan, who was a true Renaissance man of 20th century Indian Buddhism. It is one of the few translations that is made directly from the Pali by an expert in the language, rather than being translated from the English. It brings into the modern age one of the most significant texts of early Buddhism in one of the most significant languages of contemporary Buddhism.

Together with the previous publication of the first third of the MN on SuttaCentral, the typing of this text was undertaken by SuttaCentral. The project is ongoing, and we aim to eventually cover the entire translated corpus of the nikayas and Vinaya.