Adds node 18 to the pull request test runners list (#74)

Mainly to keep track of tests passing in node 18

Author: acolchado

.github/workflows/pull-request.yml

@@ -13,7 +13,7 @@ jobs:
 
     strategy:
       matrix:
-        node-version: [14.x, 16.x]
+        node-version: [14.x, 16.x, 18.x]
         # See supported Node.js release schedule at https://nodejs.org/en/about/releases/
 
     steps: