UPDATE: Adds 56 functions in the Statistical section

Uses statrs for numerical functions

REFACTOR: Put statistical functions on its own module

This might seem counter-intuitive but the wasm build after this refactor
is 1528 bytes smaller :)

base/src/test/statistical/test_fn_var.rs

@@ -0,0 +1,46 @@
+#![allow(clippy::unwrap_used)]
+
+use crate::test::util::new_empty_model;
+
+#[test]
+fn smoke_test() {
+    let mut model = new_empty_model();
+    model._set("A1", "=STDEV.P(10, 12, 23, 23, 16, 23, 21)");
+    model._set("A2", "=STDEV.S(10, 12, 23, 23, 16, 23, 21)");
+    model.evaluate();
+
+    assert_eq!(model._get_text("A1"), *"5.174505793");
+
+    assert_eq!(model._get_text("A2"), *"5.589105048");
+}
+
+#[test]
+fn numbers() {
+    let mut model = new_empty_model();
+
+    model._set("A2", "24");
+    model._set("A3", "25");
+    model._set("A4", "27");
+    model._set("A5", "23");
+    model._set("A6", "45");
+    model._set("A7", "23.5");
+    model._set("A8", "34");
+    model._set("A9", "23");
+    model._set("A10", "23");
+    model._set("A11", "TRUE");
+    model._set("A12", "'23");
+    model._set("A13", "Text");
+    model._set("A14", "FALSE");
+    model._set("A15", "45");
+
+    model._set("B1", "=VAR.P(A2:A15)");
+    model._set("B2", "=VAR.S(A2:A15)");
+    model._set("B3", "=VARA(A2:A15)");
+    model._set("B4", "=VARPA(A2:A15)");
+    model.evaluate();
+
+    assert_eq!(model._get_text("B1"), *"71.9625");
+    assert_eq!(model._get_text("B2"), *"79.958333333");
+    assert_eq!(model._get_text("B3"), *"240.248626374");
+    assert_eq!(model._get_text("B4"), *"223.088010204");
+}