'yarn serve' should run in the correct folder

the 'Running & Developing' does not specify which folder the yarn command should run, running it in the root folder does not provide the desired result. So I mention that you need to run it in 'lsp-inspector' folder.

README.md

@@ -69,7 +69,7 @@ Here is a sample:
 ```
 
 ## Running & Developing
-
+Navigate to the sub-folder `lsp-inspector`, and:
 - `yarn`
 - `yarn serve`
 
@@ -77,4 +77,4 @@ Here is a sample:
 
 Copyright (c) Microsoft Corporation. All rights reserved.
 
-Licensed under the [MIT](LICENSE) License.
+Licensed under the [MIT](LICENSE) License.