[mpk]

PlantUML supports this https://plantuml.com/handwritten

Add this to any diagram to get the effect you want,

  skinparam handwritten true
  skinparam monochrome true

Demo: https://tinyurl.com/ycdu7owa

[AlexITC]

Also, you can use https://collabuml.com to collaboratively build diagrams.

[kristiandupont]

Thank you