"unrestricted" number of custom palettes (#4932)

- allow more than 10 custom palettes
- move palettes into CPP file
- Fix for minimizing cpal.htm (saves 2k of flash)
- shortened names in cpal, saves about 400 bytes of Flash after packing
- removed async from common.js loading to prevent errors on page loads if the file is not cached
- restricted nubmer of user palettes on ESP8266 to 10
- unrestricted number of user palettes on all other platforms (total max palettes: 256)
- added a warning when adding more than 10 palettes to let the user decide to risk it
- Bugfixes in palette enumeration, fixed AR palette adding
- AR palettes are now also added if there are more than 10 custom palettes

Co-authored-by: Blaž Kristan <blaz@kristan-sp.si>

wled00/colors.cpp

@@ -252,7 +252,7 @@ void loadCustomPalettes() {
   byte tcp[72]; //support gradient palettes with up to 18 entries
   CRGBPalette16 targetPalette;
   customPalettes.clear(); // start fresh
-  for (int index = 0; index<10; index++) {
+  for (int index = 0; index < WLED_MAX_CUSTOM_PALETTES; index++) {
     char fileName[32];
     sprintf_P(fileName, PSTR("/palette%d.json"), index);