Handle missing Readme

[mattfarina]

When there is no readme (e.g., https://hub.helm.sh/charts/banzaicloud-stable/cadence) we need to handle that gracefully.

[mattfarina]

Note, this example may go away as I asked them to fix it.

[Dean-Coakley]

I may give this a shot, how would you like it handled @prydonius ?

[prydonius]

That would be great, @Dean-Coakley. The example has been fixed now, so I'm not sure, but we might just need to make sure we're catching the 404 response and rendering an error.

[mattfarina]

In handling the error it would be useful to share that no readme is available to display.