Improve `--format` flag error message

[nikitabobko]

Problem 1

Actual:

$ aerospace list-windows --all --format '%{}'
ERROR: Unknown interpolation variable ''. Possible values: window-id|window-is-fullscreen|window-title|workspace|workspace-is-focused|workspace-is-visible|monitor-id|monitor-appkit-nsscreen-screens-id|monitor-name|app-bundle-id|app-name|app-pid|app-exec-path|app-bundle-path|right-padding|newline|tab

Expected:

ERROR: Unknown interpolation variable ''.
Possible values:
    window-id
    window-is-fullscreen
    window-title
    workspace
    workspace-is-focused
    workspace-is-visible
    monitor-id
    monitor-appkit-nsscreen-screens-id
    monitor-name
    app-bundle-id
    app-name
    app-pid
    app-exec-path
    app-bundle-path
    right-padding
    newline
    tab

Problem 2

Actual:

$ aerospace list-windows --all --format
ERROR: <output-format> is mandatory

Expected:

$ aerospace list-windows --all --format
ERROR: <output-format> is mandatory.
Possible interpolation variables:
    window-id
    window-is-fullscreen
    window-title
    workspace
    workspace-is-focused
    workspace-is-visible
    monitor-id
    monitor-appkit-nsscreen-screens-id
    monitor-name
    app-bundle-id
    app-name
    app-pid
    app-exec-path
    app-bundle-path
    right-padding
    newline
    tab

Open questions

Think about possible alternative:

Possible values:
    window-id window-is-fullscreen window-title workspace workspace-is-focused workspace-is-visible
    monitor-id monitor-appkit-nsscreen-screens-id monitor-name app-bundle-id app-name app-pid
    app-exec-path app-bundle-path right-padding newline tab