Adds a cache policy for the `gi` command completion function, i.e.
`_gitignoreio`. Previously, every completion call would request the list
endpoint of gitignore.io over the network, resulting in a delay between
pressing <Tab> and the autocomplete options showing up.
Since we don't expect the gitignore.io templates to change that
frequently, configured the cache policy to expire after 7 days.
Signed-off-by: Rishvic Pushpakaran <rishvic@gmail.com>
Co-authored-by: Carlo Sala <carlosalag@protonmail.com>
