Update README.md

Author: andamian

README.md

@@ -13,7 +13,7 @@ complete LaTeX installation, a sufficiently capable `make`, preferably
 [latexmk](https://personal.psu.edu/~jcc8/software/latexmk/) and probably
 [rsvg-convert](https://wiki.gnome.org/Projects/LibRsvg). Alternatively, IVOA
 provides a Docker Image with the required enviroment already installed
-(https://github.com/ivoa/ivoatex-docker). For further
+([ivoatex-docker](https://github.com/ivoa/ivoatex-docker)). For further
 details, see [ivoatexDoc](https://ivoa.net/documents/Notes/IVOATexDoc/).
 
 This document is distributed under CC-BY-SA.