Improve storySeed initialisation

The storySeed no longer goes through the PRNG on init, and takes the
timestamp directly.

It also no longer uses modulo 100, which should give more variety.

src/engine/StoryState.ts

@@ -332,8 +332,8 @@ export class StoryState{
 		this._turnIndices = new Map();
 		this.currentTurnIndex = -1;
 
-		let timeSeed = (new Date()).getTime();
-		this.storySeed = (new PRNG(timeSeed)).next() % 100;
+		let timeSeed = Date.now();
+		this.storySeed = timeSeed;
 		this.previousRandom = 0;
 
 		this._currentChoices = [];