ci: add python 3.14 beta tests #308

Job	Run time
docs	20s
test / Python 3.10	19s
test / Python 3.13	19s
test / Python 3.14	10m 31s
test / Install [dev] on ubuntu-latest	14s
test / Install [dev] on windows-latest	48s
test / Build and inspect the package	12s
test / Build and run the docker image	42s
test / Install [dev] on macos-latest	22s
required-checks-pass	3s
	13m 50s

Provide feedback