Upgradeability checks do not recognize Hardhat

Hi There,

I tried to run the upgradeability checks (https://github.com/crytic/slither/wiki/Upgradeability-Checks) on a Hardhat project using the following command:

```bash
lither-check-upgradeability project .
```

and got this back:

```
ERROR:Slither:Invalid compilation:
project does not exist (are you in the correct directory?)
```

I also tried the same with an individual file path. Any thoughts on what I may be doing wrong here?

P.S. Using basic slither works well.