Install tfhub package (#197)

http://b/270142712

Author: Philmod

package_installs.R

@@ -64,3 +64,7 @@ install_torch()
 install_version("keras", version = "2.6.0.0", ask=FALSE)
 
 install.packages(c('collections', 'languageserver'), dependencies=TRUE)
+
+# The tfhub package is added to the rcran image.
+library(tfhub)
+install_tfhub()