added fontHeight() function with no parameter to be consistent with the textWith function and others. no parameter means default font.

TFT_eSPI.cpp

@@ -2141,6 +2141,10 @@ int16_t TFT_eSPI::fontHeight(int16_t font)
   return pgm_read_byte( &fontdata[font].height ) * textsize;
 }
 
+int16_t TFT_eSPI::fontHeight()
+{
+  return fontHeight(textfont);
+}
 
 /***************************************************************************************
 ** Function name:           drawChar

TFT_eSPI.h

@@ -631,7 +631,8 @@ class TFT_eSPI : public Print {
            textWidth(const char *string),
            textWidth(const String& string, int font),
            textWidth(const String& string),
-           fontHeight(int16_t font);
+           fontHeight(int16_t font),
+           fontHeight();
 
   void     setAddrWindow(int32_t xs, int32_t ys, int32_t xe, int32_t ye);