Support probing Astro (#1795)

This adds support for probing Astro based on eslint-plugin-astro. Probing
Astro is is enabled by default for the astro language id.

Co-authored-by: Dirk Bäumer <dirkb@microsoft.com>

Author: remcohaszing

package.json

@@ -305,6 +305,7 @@
 						"type": "string"
 					},
 					"default": [
+						"astro",
 						"javascript",
 						"javascriptreact",
 						"typescript",

server/src/eslint.ts

@@ -751,6 +751,7 @@ export namespace ESLint {
 	}();
 
 	const languageId2PluginName: Map<string, string> = new Map([
+		['astro', 'astro'],
 		['html', 'html'],
 		['json', 'jsonc'],
 		['json5', 'jsonc'],