Regex Support
Hi -

Not sure if i am doing something wrong, but i am trying to run basic regex against the http API but i am not getting results where i would expect to. I have a few examples of what i have tried below. All queries return 0 results Would you be able to take a look?

```
POST https://api.spacexdata.com/v4/cores/query
{"query":{"serial":{"$regex":"/B10/"},"options":{}}}

POST https://api.spacexdata.com/v4/cores/query
{"query":{"serial":{"$regex":"B10"},"options":{}}}

POST https://api.spacexdata.com/v4/cores/query
{"query":{"serial":"/B10/"},"options":{}}}
```

Ideally, i'd just like to use $search but i get text index errors. I imagine, you may need to do some parsing to look for $regex entries and convert them to new RegexExp() - but i haven't had a chance to look at the code.

This would be useful across all services to allow for better apps to be built.

Thanks for the awesome API you and the community have built here!