Tutorial on integrating custom blocks with Write mode

[bph]

Discussed in #330

^{Originally posted by annezazu November 4, 2024}
Considering work is expanding to bring a Write mode to fruition that greatly simplifies the editing experience, we need developers to be aware of the impact on their respective blocks, whether one off custom blocks for clients or broader blocks tied into bigger plugins. As a result, I think a dedicated tutorial on the topic that also explains the goal of write mode would be very helpful to see early in the 6.8 release cycle.

[troychaplin]

I am quite interested in this topic and would be happy to do a 1st or 2nd review when ready