Self Signed Certificate Support Doc

[Jooho]

What is changing? (Please include as many details as possible.)

There is no documentation on how to set cabundle for self-signed certificate and skip validation.

How will this impact our users?

Users who use internal registries such as Minio applied self-signed cert need to set cabundle to pull models. So far, there have been no ways to attach cabundle to storage-initializer container. Recently this feature was added to KServe so we need to explain how to use the functions that are related to the certificate.

In what release will this take happen (to the best of your knowledge)?

v0.12

Context

Link to associated PRs or issues from other repos here.

1. related issue: feat: CA bundle mount options for storage initializer kserve#3250
2. related readme: https://github.com/kserve/kserve/tree/master/docs/samples/cabundle

Additional info