Added documentation

Author: YohDeadfall

Diff for: library/alloc/src/ffi/c_str.rs

@@ -818,6 +818,9 @@ impl From<Vec<NonZero<u8>>> for CString {
 impl FromStr for CString {
     type Err = NulError;
 
+    /// Converts a string `s` into a [`CString`].
+    ///
+    /// This method is equivalent to [`CString::new`].
     #[inline]
     fn from_str(s: &str) -> Result<Self, Self::Err> {
         Self::new(s)
@@ -827,6 +830,9 @@ impl FromStr for CString {
 impl TryInto<String> for CString {
     type Error = IntoStringError;
 
+    /// Converts the `CString` into a [`String`] if it contains valid UTF-8 data.
+    ///
+    /// This method is equivalent to [`CString::into_string`].
     #[inline]
     fn try_into(self) -> Result<String, Self::Error> {
         self.into_string()