Include or generate core_version.h

[justind000]

I have run into this with a couple Arduino libraries. They expect to be able to check the ESP32 build version through this header file. Here's one as an example of what they do with it.

core_version.h is a header file with a few #defines. Mine looks like this:

#define ARDUINO_ESP32_GIT_VER 0x46386288 #define ARDUINO_ESP32_GIT_DESC 1.0.4 #define ARDUINO_ESP32_RELEASE_1_0_4 #define ARDUINO_ESP32_RELEASE "1_0_4"

You can see the mainline ESP32 Github has an install script that generates it on install here: https://github.com/espressif/arduino-esp32/blob/ed96d2a1b70ea02d925435d06b71617bd451ffec/.github/scripts/on-release.sh#L201

I just copied mine from my esp32 core install to the heltec/esp32/core/esp32 directory and things compile, but it would be nice to see it work out of the box.