docs: update demo references

Author: bennypowers

docs/docs/develop/html.md

@@ -49,7 +49,7 @@ render() {
 }
 ```
 
-We'll also need to update `/demo/pf-cool-element.html`
+We'll also need to update `/demo/index.html`
 so that the user's name is passed into the slot that we added in `pf-cool-element.ts`:
 
 ```html

elements/pf-search-input/docs/pf-search-input.md

@@ -26,7 +26,7 @@ import '@patternfly/elements/pf-search-input/pf-search-input.js';
 #### Search Input
 
 {% htmlexample %}
-  {% renderFile "./elements/pf-search-input/demo/pf-search-input.html" %}
+  {% renderFile "./elements/pf-search-input/demo/index.html" %}
 {% endhtmlexample %}
 
 #### Search Input Form

elements/pf-select/docs/pf-select.md

@@ -26,7 +26,7 @@ Focus on options using arrow keys or
 by typing the first character of an option.
 
 {% htmlexample %}
-  {% renderFile "./elements/pf-select/demo/pf-select.html" %}
+  {% renderFile "./elements/pf-select/demo/index.html" %}
 {% endhtmlexample %}
 
 #### Single with description

elements/pf-table/docs/pf-table.md

@@ -19,7 +19,7 @@
 
   Simple table using composable components
 
-  {% htmlexample src="../demo/pf-table.html" %}{% endhtmlexample %}
+  {% htmlexample src="../demo/index.html" %}{% endhtmlexample %}
 
   ### Sortable