Fix 2000/bellard/README.md

In a previous commit I had accidentally changed 'Author's remarks' to
'Alternate code' (I have no idea how this happened).

Another typo was fixed.

Added a note how this no longer (of course) prints the largest prime
known.

Fix URL.

Fix formatting.

2000/bellard/README.md

@@ -4,8 +4,7 @@
 451 chemin du mas de Matour  
 34790 Grabels  
 France  
-
+<https://bellard.org>  
-    http://www.enst.fr/~bellard
 
 ## To build:
 
@@ -27,16 +26,18 @@ Do. Or do not. There is no try. :-)
 
 ## Judges' remarks:
 
-This code is an nice compact example of a Modular Fast Fourier Transform.
+This code is a nice compact example of a Modular Fast Fourier Transform.  While
-While its output is very specific, the internal FFT has a wide variety
+its output is very specific, the internal FFT has a wide variety of uses.
-of uses.
 
 Can you modify this code to produce primes such as `23523*2^70000-1,
 48594^65536+1` or `6917!-1`?
 
-### Alternate code:
+NOTE: as bigger primes are found as time goes by this program no longer prints
+the biggest prime once noted by the author below.
 
-This program printed the biggest known prime number (2^6972593-1)
+## Author's comments:
+
+This program prints the biggest known prime number (`2^6972593-1`)
 in base 10. It requires a few minutes. It uses a Modular Fast
 Fourier Transform to compute this number in a reasonable amount
 of time (the usual method would take ages !).