Create TAM Manager READMEs section

Why is this change being made?

As part of the recommendations for transitioning to being a manager, this creates a section within the Technical Account Manager handbook area for manager READMEs.

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