Add datahub badge to README

README.md

@@ -1,4 +1,4 @@
-<a href="https://datahub.io/core/global-temp"><img src="https://badgen.net/badge/icon/View%20on%20datahub.io/orange?icon=https://datahub.io/datahub-cube-badge-icon.svg&label&scale=1.25)" alt="badge" /></a>
+<a className="gh-badge" href="https://datahub.io/core/global-temp"><img src="https://badgen.net/badge/icon/View%20on%20datahub.io/orange?icon=https://datahub.io/datahub-cube-badge-icon.svg&label&scale=1.25" alt="badge" /></a>
 
 Global Temperature Time Series. Data are included from the GISS Surface Temperature (GISTEMP) analysis and the global component of Climate at a Glance (GCAG). Two datasets are provided: 1) global monthly mean and 2) annual mean temperature anomalies in degrees Celsius from 1880 to the present as for the GCAG data is available from 1850 to the present.