Update utils.ts

Hi @j0pgrm, re #81

Your `if` statement is there to cover the possbility that your PRNG will generate the number 1. 
In general, PRNGs produce values from 0 to _less than_ 1, i.e. from the range 0 (inclusive) to 1 (exclusive). This is because when they generate an N-bit binary fraction, the highest value (all `1`s) will be just a tiny bit smaller than 1.

Your `Math.floor` correctly rounds downward, so that `rand` will be in the range 0 (inclusive) to ENCODING_LEN *- 1* (inclusive). 
So the `if` will never be triggered.

If, for some reason, you in future switch to a prng that somehow can generate a 1, for example because it has an idiosyncratic desire to cover a range of 0 (_exclusive_) to 1 (_inclusive_), then:

* the chance of this is extremely small (1 in 2**N, not 1 in 2**8)
* the PRNG will have lost the ability to generate 0
* your random character generator would have a micrscopically smaller chance of generating the first encoding character, and have a microscopic chance of trying to pick the non-existent character at #ENCODING_LEN.

A neat solution for you is to simply wrap round that exactly-1 PRNG value back to 0, most conveniently  A simple way to achieve this is to modulo the `rand` by ENCODING_LEN.



Thank you for an excellent library.

Author: darrelfrancis

source/utils.ts

@@ -2,11 +2,13 @@ import { ENCODING, ENCODING_LEN } from "./constants.js";
 import { PRNG } from "./types.js";
 
 export function randomChar(prng: PRNG): string {
-    let rand = Math.floor(prng() * ENCODING_LEN);
-    if (rand === ENCODING_LEN) {
-        rand = ENCODING_LEN - 1;
-    }
-    return ENCODING.charAt(rand);
+
+    // Currently PRNGs generate fractions from 0 to _less than_ 1, so no "%" is necessary.
+    // However, just in case a future PRNG can generate 1, 
+    // we are applying "% ENCODING LEN" to wrap back to the first character
+    
+    const randomPosition = Math.floor(prng() * ENCODING_LEN) % ENCODING_LEN; 
+    return ENCODING.charAt(randPosition);
 }
 
 export function replaceCharAt(str: string, index: number, char: string): string {