dotenv support alters json values

just version 1.40.0 (on MacOS) strips some characters out of json values in the .env file.

Example:

.env:
```
VAR={"color":"red"}
```

Justfile:
```
set dotenv-load

default:
echo $VAR
```

Output:
```
echo $VAR
{color:red}
```

Output using `npx dotenv-cli -p VAR`:
```
{"color":"red"}
```

Note how just is stripping the quotes off the key and value.

I see that just is using dotenvy. Perhaps this bug is related: https://github.com/allan2/dotenvy/issues/84

Workaround:
Putting quotes around the value in the .env file, e.g.:
```
VAR='{"color":"red"}'
```

Start with the .env and Justfile example to reproduce dotenv loading on macOS, then inspect just's dotenvy integration and the referenced dotenvy issue. Done means JSON values such as {"color":"red"} retain their quotes when loaded without requiring extra quoting.

Written by the indexing model from the issue text.