Short-circuit Liquid rendering for plain-text strings (#60522)

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: heiskr

src/content-render/liquid/index.ts

@@ -2,7 +2,9 @@ import { processLiquidPost } from './post'
 import { engine } from './engine'
 
 export async function renderLiquid(template: string, context: any): Promise<string> {
-  template = await engine.parseAndRender(template, context)
+  if (template.includes('{%') || template.includes('{{')) {
+    template = await engine.parseAndRender(template, context)
+  }
   template = processLiquidPost(template)
   return template
 }