fix cargo doc warnings (#417)

src/backends/plonky2/primitives/ec/curve.rs

@@ -42,7 +42,7 @@ type ECField = QuinticExtension<GoldilocksField>;
 /// Computes sqrt in ECField as sqrt(x) = sqrt(x^r)/x^((r-1)/2) with r
 /// = 1 + p + ... + p^4, where the numerator involves a sqrt in
 /// GoldilocksField, cf.
-/// https://github.com/pornin/ecgfp5/blob/ce059c6d1e1662db437aecbf3db6bb67fe63c716/rust/src/field.rs#L1041
+/// <https://github.com/pornin/ecgfp5/blob/ce059c6d1e1662db437aecbf3db6bb67fe63c716/rust/src/field.rs#L1041>
 pub fn ec_field_sqrt(x: &ECField) -> Option<ECField> {
     // Compute x^r.
     let x_to_the_r = (0..5)

src/backends/plonky2/primitives/ec/gates/curve.rs

@@ -41,10 +41,10 @@ use crate::backends::plonky2::{
 /// allocation of operations to gates via the `current_slots` field.  Once the circuit is fully
 /// defined, during the build the circuit the generators
 /// associated to unused operations (free slots) are removed:
-/// https://github.com/0xPolygonZero/plonky2/blob/82791c4809d6275682c34b926390ecdbdc2a5297/plonky2/src/plonk/circuit_builder.rs#L1210
+/// <https://github.com/0xPolygonZero/plonky2/blob/82791c4809d6275682c34b926390ecdbdc2a5297/plonky2/src/plonk/circuit_builder.rs#L1210>
 /// Since the generator for the unused operations are removed, no witness value will be calculated
 /// for them, and the free slots gate witness wires will be filled with the default value which is zero:
-/// https://github.com/0xPolygonZero/plonky2/blob/82791c4809d6275682c34b926390ecdbdc2a5297/plonky2/src/iop/witness.rs#L377
+/// <https://github.com/0xPolygonZero/plonky2/blob/82791c4809d6275682c34b926390ecdbdc2a5297/plonky2/src/iop/witness.rs#L377>
 /// This means that a gate with multiple operations need to pass the constraints for a single
 /// operation when all its witness wire values are zero (so that when the gate is partially used,
 /// the unused slots still pass the constraints). This is the reason why this gate doesn't add the

src/backends/plonky2/primitives/merkletree/mod.rs

@@ -1,5 +1,5 @@
 //! Module that implements the MerkleTree specified at
-//! https://0xparc.github.io/pod2/merkletree.html .
+//! <https://0xparc.github.io/pod2/merkletree.html> .
 use std::{collections::HashMap, fmt, iter::IntoIterator};
 
 use itertools::zip_eq;
@@ -14,7 +14,7 @@ pub mod error;
 pub use error::{TreeError, TreeResult};
 
 /// Implements the MerkleTree specified at
-/// https://0xparc.github.io/pod2/merkletree.html
+/// <https://0xparc.github.io/pod2/merkletree.html>
 #[derive(Clone, Debug)]
 pub struct MerkleTree {
     max_depth: usize,

src/backends/plonky2/primitives/signature/mod.rs

@@ -1,5 +1,5 @@
 //! Proof-based signatures using Plonky2 proofs, following
-//! https://eprint.iacr.org/2024/1553 .
+//! <https://eprint.iacr.org/2024/1553> .
 
 pub mod circuit;
 pub use circuit::*;