Blog post for mutating webhooks

[developer-guy]

Description

This time, we are implementing Mutating Admission Webhook as OpenFaaS Function

Types of changes

• [x] New blog post
• [x] Updating an existing blog post
• [ ] Updating part of the page page
• [ ] Adding a new web-page

Checklist:

• [x] I have given attribution for any images I have used and have permission to use them under Copyright law
• [x] My code follows the writing-style of the publication and I have checked this
• [x] I've read the CONTRIBUTION guide
• [x] I have signed-off my commits with git commit -s

[developer-guy]

Changes have been made in #200 is merged with this PR.

[alexellis]

/set title: Blog post for mutating webhooks

[developer-guy]

The basic flow is good, but the example needs work. We want users to identify with the use-case and to potentially try it out, not print hello world to the disk of every container. So please take a detailed read of the feedback and think about how we can make this something everyone will want to try.

Everything seems fine to me, I made changes according to your reviews, thank you