CI: Run on main and on request in addition to pull requests #4

Job	Run time
most-tests (native)	1h 0m 53s
rustfmt	28s
quick-examples (examples/rust-hello-world, native)	2m 57s
most-tests (sltb001a)	2h 3m 43s
quick-examples (examples/rust-hello-world, sltb001a)	3m 31s
most-tests (samr21-xpro)	1h 3m 58s
quick-examples (examples/rust-hello-world, samr21-xpro)	3m 18s
most-tests (stk3700)	2h 6m 32s
quick-examples (examples/rust-hello-world, stk3700)	3m 32s
quick-examples (examples/rust-gcoap, native)	3m 13s
quick-examples (examples/rust-gcoap, sltb001a)	3m 47s
quick-examples (examples/rust-gcoap, samr21-xpro)	3m 33s
quick-examples (examples/rust-gcoap, stk3700)	3m 56s
quick-examples (tests/rust_minimal, native)	3m 1s
quick-examples (tests/rust_minimal, sltb001a)	3m 24s
quick-examples (tests/rust_minimal, samr21-xpro)	3m 11s
quick-examples (tests/rust_minimal, stk3700)	3m 41s
	6h 56m 38s

Provide feedback