Add SG.5.06 control to handbook

Why is this change being made?

Adding the control guidance page for the new SG.5.06 (Board Bylaws) control. Additionally, the sec-controls handbook page has been updated to include a link to the control guidance page for this control.

Does this MR meet the acceptance criteria?

Assign to DRI

• 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