Add todo regarding License to checklist in Readme.

[zorp]

Add todo item to the checklist that must be completed when using the documentation template. The todo list should be expanded to include an item where the user/maintainer is reminded to reflect on the license in use. The new checklist item must take the following into account:

• Compliance with OS2 license guide, https://www.os2.eu/knowledge/article/124
• Compliance with any license on existing material that may be added to the documentation