fix syntax highlighting

Co-authored-by: danyill <[email protected]>

API.md

@@ -22,7 +22,7 @@ The **OpenSCD core API** is:
 OpenSCD core communicates the data necessary for editing SCL documents by setting the following [properties](https://developer.mozilla.org/en-US/docs/Glossary/Property/JavaScript) on the plugin's [DOM Element](https://developer.mozilla.org/en-US/docs/Web/API/HTMLElement):
 
 
-```typescript=
+```typescript
 export default class Plugin extends LitElement {
   docs: Record<string, XMLDocument> = {};
   doc?: XMLDocument;