Override minimum cache duration

[applejag]

The HTTP cache when bundling is working great, but most schema stores respond with only 5 or 30 minutes of caching. Would be nice to be able to override it to say that schemas should be cached for longer.

I propose:

helm schema --bundle-cache-min 24h

# .schema.yaml

bundleCacheMin: 24h

As a bonus would be nice to be able to set the setting to units that Go's time.Duration doesn't support, such as:

• 1d = 24h
• 1w = 7d
• 1M = 30d
• 1y = 365d