Several contraction (apostrophe) replacements failing due to word boundary

## Expected and actual behavior

```js
decontract("wouldn't've");
// expected: "would not have"
// actual: "would not've"

decontract("'cause");
// expected: "because"
// actual: "'cause"
```

## Description

The replacement logic uses Regex word boundaries, but this does not give the expected result when a word contains multiple apostrophes or end/starts with an apostrophe.


