Fix link formatting in README.md (#62)

Author: lgoettgens

README.md

@@ -7,7 +7,7 @@ The PrimGrp package provides the library of primitive permutation
 groups which includes, up to permutation isomorphism (i.e., up to
 conjugacy in the corresponding symmetric group), all primitive 
 permutation groups of degree < 8192. Groups of degree 4096 to 8191
-must be downloaded separately from https://doi.org/10.5281/zenodo.10411366
+must be downloaded separately from <https://doi.org/10.5281/zenodo.10411366>
 and then installed by following the instructions given there.
 
 It has been formerly a part of the core GAP system, and has been