Use .env.local if possible while executing cli app.

Currently the grida cli (grida) uses .env to store credentials (pat), in some cases, e.g. vercel apps, uses .env syncing with the remote server, so it is a good idea to store the credentials to .env.local. (if possible, if file already exists)

1. write: to .env.local if file already present
2. read: from .env and .env.local, overwrite .local values. (must be some libraries handling this.)