Add sanity checks for ethernet config table and WLED_ETH_DEFAULT

Small helper for integrators by compile-time sanity checks:
* WLED_NUM_ETH_TYPES is aligned with the boards table
* WLED_ETH_DEFAULT is aligned with the boards table

-> can be merged into 17.0.0, 16.0.0, and 0.15.x branch

Author: softhack007

wled00/network.cpp

@@ -177,6 +177,12 @@ const ethernet_settings ethernetBoards[] = {
   },
 };
 
+// sanity checks for ethernet config table and WLED_ETH_DEFAULT
+static_assert((sizeof(ethernetBoards)/sizeof(ethernetBoards[0])) == WLED_NUM_ETH_TYPES, "WLED_NUM_ETH_TYPES does not match size of ethernetBoards[] table.");
+#ifdef WLED_ETH_DEFAULT
+  static_assert(((WLED_ETH_DEFAULT) >= WLED_ETH_NONE) && ((WLED_ETH_DEFAULT) < WLED_NUM_ETH_TYPES), "WLED_ETH_DEFAULT is out of range.");
+#endif
+
 bool initEthernet()
 {
   static bool successfullyConfiguredEthernet = false;