Add 1.x maintenance branch to CI #129

Job	Run time
test (3.3, Gemfile, 2)	12m 10s
test (3.3, spec/support/Gemfile.rails6.1, 2)	10m 41s
test (3.3, spec/support/Gemfile.rails7, 2)	12m 52s
test (3.2, Gemfile, 2)	12m 54s
test (3.2, spec/support/Gemfile.rails6.1, 2)	10m 26s
test (3.2, spec/support/Gemfile.rails7, 2)	12m 24s
test (3.1, Gemfile, 2)	12m 43s
test (3.1, spec/support/Gemfile.rails6.1, 2)	10m 45s
test (3.1, spec/support/Gemfile.rails7, 2)	13m 5s
test (3.0, Gemfile, 2)	13m 18s
test (3.0, spec/support/Gemfile.rails6.1, 2)	10m 21s
test (3.0, spec/support/Gemfile.rails7, 2)	11m 57s
	2h 23m 36s

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