Manually update to https://github.com/lit/lit main

package.json

@@ -33,18 +33,18 @@
     "typescript",
     "lit"
   ],
-  "author": "The Polymer Authors",
+  "author": "Google LLC",
   "license": "BSD-3-Clause",
   "dependencies": {
-    "lit": "^2.0.0-pre.1",
-    "lit-element": "^3.0.0-pre.2"
+    "lit": "^2.0.0-rc.1",
+    "lit-element": "^3.0.0-rc.1"
   },
   "devDependencies": {
-    "@11ty/eleventy": "^0.10.0",
+    "@11ty/eleventy": "^0.12.1",
     "@11ty/eleventy-plugin-syntaxhighlight": "^3.0.1",
     "@esm-bundle/chai": "^4.1.5",
     "@open-wc/testing": "^2.5.32",
-    "@open-wc/testing-karma": "^3.3.11",
+    "@open-wc/testing-karma": "^4.0.9",
     "@rollup/plugin-node-resolve": "^9.0.0",
     "@rollup/plugin-replace": "^2.3.3",
     "@types/mocha": "^7.0.2",
@@ -53,9 +53,9 @@
     "@web/dev-server": "0.0.29",
     "@web/dev-server-legacy": "^0.1.4",
     "@web/dev-server-rollup": "^0.2.7",
-    "@web/test-runner": "^0.10.2",
+    "@web/test-runner": "^0.12.15",
     "@web/test-runner-mocha": "^0.3.5",
-    "@web/test-runner-playwright": "^0.5.7",
+    "@web/test-runner-playwright": "^0.8.4",
     "@webcomponents/webcomponentsjs": "^2.5.0",
     "deepmerge": "^4.2.2",
     "eslint": "^6.8.0",