Update workflow trigger to run on maitenance branches #38

Job	Run time
code-lint	13s
run-tests (3.8, ubuntu-latest)	20s
run-tests (3.8, macos-12)	31s
run-tests (3.8, macos-latest)	51s
run-tests (3.8, windows-latest)	54s
run-tests (3.11, ubuntu-latest)	25s
run-tests (3.11, macos-12)	35s
run-tests (3.11, macos-latest)	18s
run-tests (3.11, windows-latest)	41s
run-tests (pypy3.8, ubuntu-latest)	1m 12s
run-tests (pypy3.8, macos-12)	1m 27s
run-tests (pypy3.8, macos-latest)	1m 19s
run-tests (pypy3.8, windows-latest)	2m 57s
run-tests (ubuntu-20.04, 3.6)	27s
coverage	10s
build-docs	34s
	12m 54s

Provide feedback