fix markdown lints

PERFORMANCE.md

@@ -66,4 +66,4 @@ safe prime generation (256 bits)/num-primes
                         time:   [1.1444 s 1.6604 s 2.1542 s]
 safe prime generation (256 bits)/glass_pumpkin                                                                          
                         time:   [213.55 ms 432.20 ms 677.55 ms]
-```
+```

README.md

@@ -8,8 +8,8 @@
 
 [![CodeCov](https://codecov.io/gh/uutils/num-prime/branch/main/graph/badge.svg)](https://codecov.io/gh/uutils/num-prime)
 
-
 This crate provides utilities for prime number related functionalities:
+
 - Primality testing
   - Deterministic primality check of `u64` integers (using a very fast hashing algorithm)
   - Fermat probable prime test

ROADMAP.md

@@ -1,20 +1,24 @@
-# Roadmap for v0.next
+## Roadmap for v0.next
+
 - Implement SIQS
 - Euler totient
 - support `primal` as backend
 
-# Roadmap for v1
+## Roadmap for v1
+
 - Support modular integer in a unified API
 - Stablize API, determine minimal verison for each dependency
 - Support no_std
 - Split the nt_funcs, factor and primality modules into sub files, and put the tables into the related files.
 
-# Undetermined
+## Undetermined
+
 - Use NumAssign as trait bounds and see if there's prominent performance improvement
 - Support `rug` and `ibig` as backend
 - Support `rug` & `primal` or `primesieve-sys` as PrimeBuffer backend
 - Support async and multi-thread
 - Implement factorization for Gaussian integers (and other quadratic integers?)
 
-# Not in plan
+## Not in plan
+
 - Support number field sieve factorization (this is efficient only for very larg numbers)