improve errors and "panics" documentation

src/commit.rs

@@ -53,7 +53,8 @@ impl<const N: usize, F: FftField, H: Hasher> FriCommitments<N, F, H> {
     /// See [`crate::commit_polynomial`] for information about the other parameters.
     ///
     /// # Panics
-    /// This may either panic or have unspecified behaviour if `remainder_degree_plus_one` is inconsistent with
+    /// - `N` must be a power of 2
+    /// - This may either panic or have unspecified behaviour if `remainder_degree_plus_one` is inconsistent with
     /// the degree-bound of the polynomial and the folding factor, or if `F` does not contain a subgroup of size
     /// `evaluations.len()`.
     pub fn new<R>(