Improvement to default task setting for providing environment variables

[michal-ko]

Currently when we run zed: open tasks the defaults for providing environment variables look as such:

// Env overrides for the command, will be appended to the terminal's environment from the settings.
    "env": { "foo": "bar" }

To better represent standard way environment variables usually look, I would like to propose to capitalise the keys. I would also like to add one more kay pair to make it clear how to provide more than one env var

// Env overrides for the command, will be appended to the terminal's environment variables from the settings.
    "env": { "FOO": "bar",  "FOO_2": "bar_2"}