feat: add --report-dir alias (for consistency with nyc)

Author: bcoe

lib/parse-args.js

@@ -16,7 +16,7 @@ function buildYargs (withCommands = false) {
       default: 'text'
     })
     .option('reports-dir', {
-      alias: 'o',
+      alias: ['o', 'report-dir'],
       describe: 'directory where coverage reports will be output to',
       default: './coverage'
     })