Update index.html.md Custom Deck Requirements

Why is this change being made?

TO show the importance of the custom deck in commercial sales and to detail the requirements

Does this MR meet the acceptance criteria?

yes

Assign to DRI

yes

• Did you assign this change to the correct DRI of the page or information you are changing?

Conformity

• Added description to this MR explaining the reasons for the proposed change, per say-why-not-just-what