remove external option

Author: Rich-Harris

packages/svelte/messages/compile-errors/template.md

@@ -324,7 +324,7 @@ HTML restricts where certain elements can appear. In case of a violation the bro
 
 ## svelte_options_invalid_attribute_value
 
-> Valid values are %list%
+> Value must be %list%, if specified
 
 ## svelte_options_invalid_customelement
 

packages/svelte/src/compiler/phases/1-parse/read/options.js

@@ -178,10 +178,10 @@ export default function read_options(node) {
 			case 'css': {
 				const value = get_static_value(attribute);
 
-				if (value === 'injected' || value === 'external') {
+				if (value === 'injected') {
 					component_options.css = value;
 				} else {
-					e.svelte_options_invalid_attribute_value(attribute, `"injected", "external"`);
+					e.svelte_options_invalid_attribute_value(attribute, `"injected"`);
 				}
 
 				break;

packages/svelte/src/compiler/types/template.d.ts

@@ -75,7 +75,7 @@ export interface SvelteOptions {
 	accessors?: boolean;
 	preserveWhitespace?: boolean;
 	namespace?: Namespace;
-	css?: 'injected' | 'external';
+	css?: 'injected';
 	customElement?: {
 		tag: string;
 		shadow?: 'open' | 'none';