Bump version to 4.18.0

Author: valeros

platform.json

@@ -19,7 +19,7 @@
     "type": "git",
     "url": "https://github.com/platformio/platform-teensy.git"
   },
-  "version": "4.17.0",
+  "version": "4.18.0",
   "frameworks": {
     "arduino": {
       "package": "framework-arduinoteensy",