High Advisory On npm audit

### Details of Audit

On 17th August 2020, there was been a security issue that was raised with `url-regex`. Details are as follows:

```
High Regular Expression Denial of Service

Package url-regex

Patched in No patch available

Dependency of backstopjs [dev]

Path backstopjs > merge-img > jimp > url-regex

More info https://npmjs.com/advisories/1550
```

Unfortunately, backstopjs is last in the queue for updates as awaiting for the following to be completed:

https://github.com/oliver-moran/jimp/issues/926
https://github.com/preco21/merge-img/issues/15

## Replication Steps

Run npm audit
Notice the "high" severity vulnerability

Run npm audit and inspect the dependency path backstopjs > merge-img > jimp > url-regex. Read npm advisory 1550 and the linked jimp issue 926 and merge-img issue 15 to determine whether upstream changes are available. Done means the high-severity url-regex advisory is no longer reported for backstopjs.

Written by the indexing model from the issue text.