deprecated commands (#4405)

* deprecated commands

* deprecated insert command

crates/nu-command/src/deprecated/mod.rs

@@ -0,0 +1,17 @@
+mod insert;
+mod nth;
+mod pivot;
+mod str_decimal;
+mod str_int;
+
+pub use insert::InsertDeprecated;
+pub use nth::NthDeprecated;
+pub use pivot::PivotDeprecated;
+pub use str_decimal::StrDecimalDeprecated;
+pub use str_int::StrIntDeprecated;
+
+#[cfg(feature = "dataframe")]
+mod dataframe;
+
+#[cfg(feature = "dataframe")]
+pub use dataframe::DataframeDeprecated;