Serve webviews from the same origin

Normally webviews are served from vscode-webview.net but we would rather them be
self-hosted.

When doing this CSP will block resources (for example when viewing images) so
add 'self' to the CSP to fix that.

Index: code-server/lib/vscode/src/vs/workbench/services/environment/browser/environmentService.ts
===================================================================
--- code-server.orig/lib/vscode/src/vs/workbench/services/environment/browser/environmentService.ts
+++ code-server/lib/vscode/src/vs/workbench/services/environment/browser/environmentService.ts
@@ -176,7 +176,7 @@ export class BrowserWorkbenchEnvironment
 
 	@memoize
 	get webviewExternalEndpoint(): string {
-		const endpoint = this.options.webviewEndpoint
+		const endpoint = (this.options.webviewEndpoint && new URL(this.options.webviewEndpoint, window.location.toString()).toString())
 			|| this.productService.webviewContentExternalBaseUrlTemplate
 			|| 'https://{{uuid}}.vscode-webview.net/{{quality}}/{{commit}}/out/vs/workbench/contrib/webview/browser/pre/';
 
Index: code-server/lib/vscode/src/vs/server/node/webClientServer.ts
===================================================================
--- code-server.orig/lib/vscode/src/vs/server/node/webClientServer.ts
+++ code-server/lib/vscode/src/vs/server/node/webClientServer.ts
@@ -280,6 +280,7 @@ export class WebClientServer {
 		const data = (await util.promisify(fs.readFile)(filePath)).toString()
 			.replace('{{WORKBENCH_WEB_CONFIGURATION}}', escapeAttribute(JSON.stringify({
 				remoteAuthority,
+				webviewEndpoint: vscodeBase + '/static/out/vs/workbench/contrib/webview/browser/pre',
 				_wrapWebWorkerExtHostInIframe,
 				developmentOptions: { enableSmokeTestDriver: this._environmentService.driverHandle === 'web' ? true : undefined },
 				settingsSyncOptions: !this._environmentService.isBuilt && this._environmentService.args['enable-sync'] ? { enabled: true } : undefined,
Index: code-server/lib/vscode/src/vs/workbench/common/webview.ts
===================================================================
--- code-server.orig/lib/vscode/src/vs/workbench/common/webview.ts
+++ code-server/lib/vscode/src/vs/workbench/common/webview.ts
@@ -24,7 +24,7 @@ export const webviewResourceBaseHost = '
 
 export const webviewRootResourceAuthority = `vscode-resource.${webviewResourceBaseHost}`;
 
-export const webviewGenericCspSource = `https://*.${webviewResourceBaseHost}`;
+export const webviewGenericCspSource = `'self' https://*.${webviewResourceBaseHost}`;
 
 /**
  * Construct a uri that can load resources inside a webview