add proper pattern validation

client/components/combobox.jsx

@@ -14,7 +14,7 @@ const Combobox = ({
 		suggestMethod           : 'includes',
 		filterOn                : []  // should allow as array to filter on multiple attributes, or even custom filter
 	},
-	valuePatterns = /.+/,
+	valuePatterns = '.+',
 	options = [],
 	keepValueOnClose = false,
 	...props

client/homebrew/editor/metadataEditor/metadataEditor.jsx

@@ -264,6 +264,7 @@ const MetadataEditor = ({
 					defaultValue={metadata.lang || ''}
 					keepValueOnClose={true}
 					placeholder='en'
+					valuePatterns="^[a-z]{2,3}(-[A-Z][a-z]{3})?(-[A-Z]{2})?$"
 					onSelect={(value)=>handleLanguage(value)}
 					onEntry={(e)=>{
 						e.target.setCustomValidity('');	//Clear the validation popup while typing