More easily Plot Trades or Trade Signals

Is your feature request related to a problem? Please describe.
Your addplot.ipynb page is phenomenal and I was able to figure out that I can add scatter points by;

1. Making a numpy array empty/zero
   trs = np.zeros((length_to_add, 1))
2. Filling it with Nans
   trs.fill(np.nan)
3. Setting my 2 scatter points as I know the index (x) and y values
   trs[x] = y
4. Adding this to a dataframe
   toplot.insert(6, "trades", trs, True)
5. Then using your well documented addplot:
   apdict = mpf.make_addplot(toplot['trades'],scatter=True,secondary_y=False)
   mpf.plot(toplot,type='candle',volume=True,addplot=apdict)

Describe the solution you'd like
While this is great it took a lot of energy - I'm moving from the plotpy (for the candles!) and there I simply wrote:
plt.scatter(trade_list_idx,trade_list_price,c='b')

Which was simpler than messing around with a dataframe and so on.

まず addplot.ipynb と、issue に示されている documented な make_addplot の呼び出しを確認し、次に既存の plotting のエントリーポイントを調べて、addplot データがどのように受け付けられているかを確認します。完了時には、説明されている NumPy array と dataframe の準備を必要とせずに、trade または signal の座標を直接プロットする、より簡単な方法を提供できるようにします。