fix: validate version with prerelease at publish time

Closes: #425

src/publish.ts

@@ -1,5 +1,6 @@
 import * as fs from 'fs';
 import { promisify } from 'util';
+import * as semver from 'semver';
 import { ExtensionQueryFlags, PublishedExtension } from 'azure-devops-node-api/interfaces/GalleryInterfaces';
 import { pack, readManifest, versionBump, prepublish } from './package';
 import * as tmp from 'tmp';
@@ -81,6 +82,10 @@ async function _publish(packagePath: string, manifest: Manifest, options: IInter
 		throw new Error("Extensions using proposed API (enableProposedApi: true) can't be published to the Marketplace");
 	}
 
+	if (semver.prerelease(manifest.version)) {
+		throw new Error(`The VS Marketplace doesn't support prerelease versions: '${manifest.version}'`);
+	}
+
 	const pat = options.pat ?? (await getPublisher(manifest.publisher)).pat;
 	const api = await getGalleryAPI(pat);
 	const packageStream = fs.createReadStream(packagePath);