fix: use 'folder: false' to use bs-local with an internal server

Author: pimlie

docs/API.md

@@ -65,8 +65,8 @@ Your browserstack user name<br/>
 - `key` (_string_)<br/>
 Your browserstack key<br/>
 > for security reasons it is recommended to use the env var `BROWSERSTACK_KEY` instead
-- `folder` (_string_, optional)<br/>
-The path to the folder which should be accessible through the browserstack-local tunnel. If not provided the default `folder` browser config option is used
+- `folder` (_string_, _boolean_ optional)<br/>
+The path to the folder which should be accessible through the browserstack-local tunnel. Explicitly set this to `false` if you wish to test an internal server. If any other falsy value is provided the default `folder` browser config option is used.
 
 ## Browser methods
 

src/utils/commands/browserstack-local.js

@@ -19,7 +19,7 @@ export default class BrowserStackLocal {
 
   static async start(config = {}) {
     // TODO: support webserver
-    if (!config.folder) {
+    if (!config.folder && config.folder !== false) {
       config.folder = path.resolve(process.cwd())
     }