Add licence in pom.xml file using tools.build

[practicalli-johnny]

Clojars requires all new projects to include a licence name within the pom.xml file (as of 29th September 2023)

Existing projects have until the end of 2023 to include a license.

Add section on using tools.build to publish Clojure libraries to Clojars.org that supports the recent requirement to include a license.

References

https://ask.clojure.org/index.php/13341/is-tools-build-considering-adding-a-license-argument