Update images, fix extrapath (#723)

* fix: typo

* fix: remove debug for git references

it generates a massive amount of logs

* feat: read values from env

allows to test act on GHA when it's not a main repo

* fix: merge extrapath with PATH

* fix(tests): add additional shells for testing

* fix(image): update images

pin node to major version only, current node version: 12.22.1
replace most images with `node:12-buster-slim` to prevent
errors on macOS runner due to DockerHub pull limit
replace ocaml image

Co-authored-by: Casey Lee <cplee@nektos.com>

pkg/runner/step_context_test.go

@@ -9,7 +9,7 @@ import (
 
 func TestStepContextExecutor(t *testing.T) {
 	platforms := map[string]string{
-		"ubuntu-latest": "node:12.20.1-buster-slim",
+		"ubuntu-latest": baseImage,
 	}
 	tables := []TestJobFileInfo{
 		{"testdata", "uses-and-run-in-one-step", "push", "Invalid run/uses syntax for job:test step:Test", platforms, ""},