feat: Validate GitHub Actions schema (#2416)

* feat: Validate GitHub Actions schema

**BREAKING** previously accepted workflows are now invalid

* update code

* fix tests

* Bump docker / fix lint

* fix test action due to moving the file

* remove unused function

* fix parsing additional functions

* fix allow int

* update docker dep, due to linter

pkg/model/action.go

@@ -5,6 +5,7 @@ import (
 	"io"
 	"strings"
 
+	"github.com/nektos/act/pkg/schema"
 	"gopkg.in/yaml.v3"
 )
 
@@ -78,6 +79,18 @@ type Action struct {
 	} `yaml:"branding"`
 }
 
+func (a *Action) UnmarshalYAML(node *yaml.Node) error {
+	// Validate the schema before deserializing it into our model
+	if err := (&schema.Node{
+		Definition: "action-root",
+		Schema:     schema.GetActionSchema(),
+	}).UnmarshalYAML(node); err != nil {
+		return err
+	}
+	type ActionDefault Action
+	return node.Decode((*ActionDefault)(a))
+}
+
 // Input parameters allow you to specify data that the action expects to use during runtime. GitHub stores input parameters as environment variables. Input ids with uppercase letters are converted to lowercase during runtime. We recommended using lowercase input ids.
 type Input struct {
 	Description string `yaml:"description"`