zed_extension_api: Fork new version of extension API (#44025)

This PR forks a new version of the `zed_extension_api` in preparation
for new changes.

We're jumping from v0.6.0 to v0.8.0 for the WIT because we released
v0.7.0 of the `zed_extension_api` without any WIT changes (it probably
should have been v0.6.1, instead).

Release Notes:

- N/A

crates/extension_api/wit/since_v0.8.0/nodejs.wit

@@ -0,0 +1,13 @@
+interface nodejs {
+    /// Returns the path to the Node binary used by Zed.
+    node-binary-path: func() -> result<string, string>;
+
+    /// Returns the latest version of the given NPM package.
+    npm-package-latest-version: func(package-name: string) -> result<string, string>;
+
+    /// Returns the installed version of the given NPM package, if it exists.
+    npm-package-installed-version: func(package-name: string) -> result<option<string>, string>;
+
+    /// Installs the specified NPM package.
+    npm-install-package: func(package-name: string, version: string) -> result<_, string>;
+}