Add Description Change History speedrun

Why is this change being made?

To bring more visibility to our speedruns, we're putting them on the Plan Page in the handbook.

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