fix standard from desc yaml, allow yml files for append target

README.md

@@ -60,7 +60,11 @@ learn help
 
 ## Get Started: Walkthrough
 
-Visit [Guru](https://app.getguru.com/boards/iEdB57dT/Creating-Content-in-Learn) for a short walkthrough to publish your first curriculum.
+You can generate a sample piece of curriculum to begin a walkthrough of how to develop curriculum with Learn with
+
+```
+learn walkthrough
+```
 
 ### Get Started: Quick Edits to Existing Curriculum
 

app/cmd/config.go

@@ -578,6 +578,7 @@ func newStandard(unitDir, unit string) Standard {
 		return standardFromUnit(unit)
 	} else {
 		// read yaml contents of file
+		//return standardFromUnit(unit)
 		standard := Standard{}
 		if err = yaml.NewDecoder(bytes.NewReader(yamlBytes)).Decode(&standard); err != nil {
 			return standardFromUnit(unit)

app/cmd/markdown.go

@@ -102,8 +102,8 @@ func (t temp) appendContent(target string) error {
 	if Minimal {
 		template = t.MinTemplate
 	}
-	if !strings.HasSuffix(target, ".md") {
-		return fmt.Errorf("'%s' must have an `.md` extension to append %s content.\n", target, t.Name)
+	if !(strings.HasSuffix(target, ".md") || strings.HasSuffix(target, ".yaml") || strings.HasSuffix(target, ".yml")) {
+		return fmt.Errorf("'%s' must have an `.md`, `.yml`, or `.yaml` extension to append %s content.\n", target, t.Name)
 	}
 
 	targetInfo, err := os.Stat(target)