Add citation file

[k4rtik]

Unsure if one should point to the precise URL with the anchor #q-language as I have done in the URL field. Suggestions welcome.

(also added an entry in the QPL Bib)

[filipw]

This is how I cited it 😅

@misc{qsharpSpec2021, author = {Microsoft}, title = {Q# Language Specification}, howpublished = {\url{https://github.com/microsoft/qsharp-language/tree/main/Specifications/Language}}, year = {2021}, note = {Accessed: 2021-12-30} }