enhance action create with env variables

**Describe the bug**
This was missed in the recently merged PR #103. The `-P` flag is overloaded to mean read params from file and read env from file. This is a copy/paste bug, the intent was to use `-E`.

https://github.com/adobe/aio-cli-plugin-runtime/pull/103/files#diff-6d51d7a8679a906a9bfdaf1a8b017006R207

Thanks to @purplecabbage for pointing this out. We were both surprised oclif didn't barf at this.

As an enhancement, Jesse also suggested supporting reading the value of an env var from the shell environemnt, so that you can do `... action create myAction -e FOO` which is syntactic sugar for `... action create myAction -e FOO $FOO`. I think this is neat/convenient (perhaps to be considered separately as an enhancement).

Esamina la gestione delle opzioni di action create nella posizione collegata in PR #103, concentrandoti sul flag -P sovraccarico e sul flag -E previsto. Conferma il comportamento esistente del file dei parametri, quindi determina se la ricerca nell’ambiente della shell è inclusa o trattata separatamente; il lavoro è completato quando i flag hanno comportamenti distinti e l’uso del comando richiesto è coperto dai test.

Scritto dal modello di indicizzazione a partire dal testo della issue.