feature: ISC License

[jbmoelker]

Changes

Adds ISC License. Based on discussions with @Siilwyn and @WesselSmit. Decided CLA is too much of a hassle to protect Voorhoede IP. So simplified to a permissive modern license.

Associated issue

Resolves #69

How to test

Review license and verify it provides what we want.

Checklist

• [x] I have performed a self-review of my own code
• [x] I have made sure that my PR is easy to review (not too big, includes comments)
• [x] I have made updated relevant documentation files (in project README, docs/, etc)
• I have added a decision log entry if the change affects the architecture or changes a significant technology
• I have notified a reviewer (co-authored)