Added BibTeX syntax tests

tests/syntax-tests/source/BibTeX/test.bib

@@ -0,0 +1,18 @@
+@book{knuth1997art,
+  title={The art of computer programming},
+  author={Knuth, Donald Ervin},
+  volume={3},
+  year={1997},
+  publisher={Pearson Education}
+}
+
+@article{egholm1993pna,
+  title={PNA hybridizes to complementary oligonucleotides obeying the Watson--Crick hydrogen-bonding rules},
+  author={Egholm, Michael and Buchardt, Ole and Christensen, Leif and Behrens, Carsten and Freier, Susan M and Driver, David A and Berg, Rolf H and Kim, Seog K and Norden, Bengt and Nielsen, Peter E},
+  journal={Nature},
+  volume={365},
+  number={6446},
+  pages={566--568},
+  year={1993},
+  publisher={Springer}
+}