* Add const char* content to ESP8266WebSerer::send()
Supercedes #3492
Allow sending raw binary data or strings directly without conversion to
a String to reduce memory overhead when possible.
From original @timw1971 PR #3492
Added public functions to allow content to be uploaded using const
char*. For some cases, this can remove the need for content to be copied
into a String, and thus can be considerably more space-efficient.
* Fix example formatting
* Make GIF example use static const array
* Make the example really need to use const char*
Make the generated GIF dynamic in the example and move the original to
PROGMEM (since that's where const arrays like this belong).