website: Make apply's usage of plan options harder to miss
website: Make apply's usage of plan options harder to miss

- I'm using distinct subheaders and smaller paragraphs to try and make the info
  about apply's two modes more skimmable.

- I'm also adding a separate "Plan Options" subheader (and keeping the section
  tiny so it stays snugged up right next to the "Apply Options" one) to make it
  extra-clear that Hey, There's More Options, They're Over There.

tommynsong/terraform,rnaveiras/terraform,rnaveiras/terraform,hashicorp/terraform,ewbankkit/terraform,ewbankkit/terraform,ewbankkit/terraform,tommynsong/terraform,hashicorp/terraform,tommynsong/terraform,ewbankkit/terraform,hashicorp/terraform,rnaveiras/terraform