Move snake case method to heck

crates/stdx/src/lib.rs

@@ -102,3 +102,17 @@ pub fn timeit(label: &'static str) -> impl Drop {
 
     Guard { label, start: Instant::now() }
 }
+
+pub fn to_lower_snake_case(s: &str) -> String {
+    let mut buf = String::with_capacity(s.len());
+    let mut prev = false;
+    for c in s.chars() {
+        if c.is_ascii_uppercase() && prev {
+            buf.push('_')
+        }
+        prev = true;
+
+        buf.push(c.to_ascii_lowercase());
+    }
+    buf
+}