Update licensing to include CC BY-SA for contents

[nweldev]

🙏 thx @vlamy for raising this issue

"Open Content" projects lack a clear indication of a by default license for non-code contents.

Context

We already defined this in blindnet.dev, with a dual MIT / CC BY-SA license.

This issue is here to enforce this decision for all blindnet contents.

Sub-tasks

• update / extend DR 0001 - Choose by default license(s) for Open Source projects to add CC BY-SA
• clearly indicate when and why to specify a specific license for a specific content
• clearly indicate this by default dual licensing in all Open Content repositories
  • https://github.com/blindnet-io/openness-framework
  • https://github.com/blindnet-io/devrel-management
  • https://github.com/blindnet-io/product-management