Upgrade to Doks v1.0.0 about website

[pavangudiwada]

@simonpasquier I attempted the update, tried a bunch of times but always had some issues. Should be fairly easy for someone familiar with JS. Here are some changes,

1. The alert short code should be changed to callout note.

Old - {{< alert icon="👉" text="Prometheus Operator requires use of Kubernetes v1.16.x and up."/>}}
New - {{< callout note >}} Prometheus Operator requires use of Kubernetes v1.16.x and up. {{</ callout >}}

2. External images are not yet supported. I believe there are very few images and it could be handled easily.

[Ayush9026]

/assign @Ayush9026 i'll solve this.