Added update command

[petarjuki7]

App update command

[MatejVukosav]

Gj! Can you also add to the docs how to use it?

[miraclx]

so.. we need the following:

$ meroctl context update --context-id <context-id> -a <application-id> --as <identity>
# one-off update

$ meroctl context update --context-id <context-id> --path ./path/to/file --as <identity>
# one-off update

$ meroctl context update --context-id <context-id> --path ./path/to/file --watch --as <identity>
# recurring update

see the call command for how identity is managed

<application-id> and <path> are mutually exclusive, and --watch should only be allowed when --path is present.