Add support to override env from apify.json

[drobnikj]

Users want to override to env attribute in apify.json for local actors runs.

• add support for file apify.local.json, where user can override env for local runs
• decribe it into readme

[B4nan]

The environmentVariables option seems to be already supported in apify run (https://github.com/apify/apify-cli/blob/master/src/commands/run.ts#L143C26-L143C46), so only thing that's missing is being able to override the path to the actor.json which is now hardcoded.