add buy me a coffee button :)

README.md

@@ -1,6 +1,7 @@
 # coverage-gutters
 [![Build Status](https://travis-ci.org/ryanluker/vscode-coverage-gutters.svg?branch=master)](https://travis-ci.org/ryanluker/vscode-coverage-gutters)
 [![Build status](https://ci.appveyor.com/api/projects/status/8vb8t787frcqtrm7?svg=true)](https://ci.appveyor.com/project/ryanluker/vscode-coverage-gutters)
+[![Buy me a coffee](https://www.paypalobjects.com/en_US/i/btn/btn_donate_SM.gif)](https://www.paypal.com/cgi-bin/webscr?cmd=_donations&business=XRWWCAZBYB9SG&lc=CA&item_name=vscode%2dcoverage%2dgutters&currency_code=CAD&bn=PP%2dDonationsBF%3abtn_donate_SM%2egif%3aNonHostedGuest)
 
 ## Features
 - watch editors and lcov feature activated via status bar button or command