feat(shortcode): added markdown attribute support for headers (#851)

docs: added "no-step-marker" example for steps

docs/content/docs/guide/shortcodes/steps.md

@@ -4,6 +4,8 @@ title: Steps
 
 A built-in component to display a series of steps.
 
+You can use the Markdown attribute `{class="no-step-marker"}` to prevent a heading from being counted as a step.
+
 ## Example
 
 {{% steps %}}
@@ -16,6 +18,10 @@ This is the first step.
 
 This is the second step.
 
+#### Step subheading {class="no-step-marker"}
+
+This will not be counted as a step.
+
 ### Step 3
 
 This is the third step.
@@ -43,5 +49,9 @@ This is the first step.
 
 This is the second step.
 
+#### Step subheading {class="no-step-marker"}
+
+This will not be counted as a step.
+
 {{%/* /steps */%}}
 ```

docs/hugo_stats.json

@@ -715,6 +715,7 @@
       "msupsub",
       "mtable",
       "mtight",
+      "no-step-marker",
       "not-prose",
       "nulldelimiter",
       "op-symbol",

layouts/_markup/render-heading.html

@@ -1,4 +1,4 @@
-<h{{ .Level }}>
+<h{{ .Level }} {{- with .Attributes.class }} class="{{ . }}" {{- end }}>
   {{- .Text | safeHTML -}}
   {{- if gt .Level 1 -}}
     <span class="hx:absolute hx:-mt-20" id="{{ .Anchor | safeURL }}"></span>