dev CLI should automatically load `dev.vars` file as an env var

[ericallam]

Should be added to the list here:

https://github.com/triggerdotdev/trigger.dev/blob/35c8e35674c9776381eedfe6d1e25c4edd8ca12b/packages/cli-v3/src/utilities/dotEnv.ts/#L5

[harshsbhat]

On it