feat: add overlap studies wrappers and align indicator API names

- add TA-Lib bindings and loader registrations for overlap studies:
  TA_ACCBANDS, TA_BBANDS, TA_DEMA, TA_EMA, TA_HT_TRENDLINE, TA_KAMA
- add new public wrappers in overlap_studies.go:
  AccBands, BBands, DEMA, EMA, HT_TRENDLINE, KAMA
- refactor momentum wrapper names to consistent Go-style exports
  (e.g. Aroon/AroonOsc, MACDExt/MACDFix, Stoch/StochF/StochRSI,
  MinusDI/MinusDM, PlusDI/PlusDM, Trix, UltOsc, WillR)
- rename MAType constants to MA_* for clearer namespacing
- update README to reflect the current exported API and overlap coverage

loader.go

@@ -95,6 +95,13 @@ func Load() (uintptr, error) {
 	purego.RegisterLibFunc(&ultosc, ptr, "TA_ULTOSC")
 	purego.RegisterLibFunc(&willr, ptr, "TA_WILLR")
 
+	purego.RegisterLibFunc(&accbands, ptr, "TA_ACCBANDS")
+	purego.RegisterLibFunc(&bbands, ptr, "TA_BBANDS")
+	purego.RegisterLibFunc(&dema, ptr, "TA_DEMA")
+	purego.RegisterLibFunc(&ema, ptr, "TA_EMA")
+	purego.RegisterLibFunc(&ht_trendline, ptr, "TA_HT_TRENDLINE")
+	purego.RegisterLibFunc(&kama, ptr, "TA_KAMA")
+
 	return ptr, nil
 }