GHSA-hfrv-h3q8-9jpr

### Summary An unsafe sanitization of dataset contents on the `MarkovData#getNext` method used in `Markov#generate` and `Markov#choose` allows a maliciously crafted string on the dataset to throw and stop the function from running properly.

### Details https://github.com/xiboon/kurwov/blob/0d58dfa42135ab40e830e92622857282f980ca89/src/MarkovData.ts#L38-L44

If a string contains a forbidden substring (i.e. `__proto__`) followed by a space character, the second line will access a special property in `MarkovData#finalData` by removing the last character of the string, bypassing the dataset sanitization (as it is supposed to be already sanitized before this function is called).

`data` is then defined as the special function found in its prototype instead of an array.

On the last line, `data` is then indexed by a random number, which is supposed to return a string but returns undefined as it's a function. Calling `endsWith` then throws.

### PoC https://runkit.com/embed/m6uu40r5ja9b

### Impact Any dataset can be contaminated with the substring making it unable to properly generate anything in some cases.