Allow valet share to support multiple domains from same app

This PR allows passing a specific domain name to `valet share` in order to have the app be served for that domain.
Now how it works is this:
- (NEW) if a domain name is passed, it checks whether it matches a link (which would be required for multiple domains served by same app project), and uses that
- if a domain name is NOT passed, it looks up any links for current directory, and uses the first found link
- else falls back to current project foldername

It also still allows passing through custom ngrok parameters if desired (ref: #112), as either the 2nd parameter (no domain name passed) or (NEW) 3rd parameter

Fixes #537

cli/scripts/fetch-share-url.sh

@@ -2,4 +2,4 @@
 
 DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
 
-php $DIR/../valet.php fetch-share-url | pbcopy
+php $DIR/../valet.php fetch-share-url $1 | pbcopy