Add snippet tags. (#8042)

This fixes the current build warnings.

Author: BillWagner

snippets/fsharp/System/TupleT1,T2,T3,T4,T5,T6,T7,TRest/Item1/item1.fs

@@ -1,5 +1,6 @@
 open System
 
+// <Snippet1>
 let showPopulation year newPopulation =
     printfn $"""{year,5}  {newPopulation,14:N0}  {"n/a",10:P2}"""
 
@@ -64,4 +65,5 @@ do
 //    1970       1,511,462     -0.95 %
 //    1980       1,203,339     -2.04 %
 //    1990       1,027,974     -1.46 %
-//    2000         951,270     -0.75 %
+//    2000         951,270     -0.75 %
+// </Snippet1>