v1.3.16 -- version submitted to bioRxiv

The pre-print for spatialLIBD is now available through bioRxiv at https://www.biorxiv.org/content/10.1101/2021.04.29.440149v1.

spatialLIBD: initial Bioconductor submission

This is the version of the spatialLIBD project at the state that we submitted it to Bioconductor for review Bioconductor/Contributions#1389.