⚡️ Accept array of string as valid input schema path. (#134)

* ⚡️ Fixes #88. Accept array of string as valid input schema path.

generate/stringlist.go

@@ -0,0 +1,33 @@
+package generate
+
+// StringList provides yaml unmarshaler to accept both `string` and `[]string` as a valid type.
+// Sourced from:
+//		https://github.com/99designs/gqlgen/blob/1a0b19feff6f02d2af6631c9d847bc243f8ede39/codegen/config/config.go#L302-L329
+type StringList []string
+
+func (a *StringList) UnmarshalYAML(unmarshal func(interface{}) error) error {
+	var single string
+	err := unmarshal(&single)
+	if err == nil {
+		*a = []string{single}
+		return nil
+	}
+
+	var multi []string
+	err = unmarshal(&multi)
+	if err != nil {
+		return err
+	}
+
+	*a = multi
+	return nil
+}
+
+func (a StringList) Has(file string) bool {
+	for _, existing := range a {
+		if existing == file {
+			return true
+		}
+	}
+	return false
+}