As a user I'd like to navigate the list of charts using the arrow keys

[adietish]

follows up on #590

Steps:

1. ASSERT: have a cluster that you're logged into
2. EXEC: in the context menu to the cluster node (in the resource tree), pick "Open Helm Charts"
3. EXEC: try to navigate the list/table of charts using the arrow keys

Result: Nothing happens.

Expected result: The next chart in the list should be selected when I press arrow down (and the previous when I press arrow up)