Add add::add_tag()

libimagtag/src/add.rs

@@ -0,0 +1,8 @@
+use libimagstore::store::Entry;
+
+use result::Result;
+use tag::Tag;
+pub fn add_tag(e: &mut Entry, t: &Tag) -> Result<()> {
+
+    unimplemented!()
+}