update README and add qrcode detect

Author: JimmyHHua

Diff for: README.md

@@ -157,4 +157,5 @@ code_115 | [KNN-Train Data Save and Load](python/code_115)   | ✔️
 code_116 | [Decision Tree Algorithm](python/code_116)   | ✔️
 code_117 | [Image Mean-shift Segmentation](python/code_117)   | ✔️
 code_118 | [Grabcut-Image Segmentation](python/code_118)   | ✔️
-code_119 | [Grabcut-Background Change](python/code_119)   | ✏️
+code_119 | [Grabcut-Background Change](python/code_119)   | ✏️
+code_120 | [Qrcode detect and decode](python/code_120)   | ✔️

Diff for: README_CN.md

@@ -156,4 +156,5 @@ code_115 | [KNN 数据保存](python/code_115)   | ✔️
 code_116 | [决策树算法](python/code_116)   | ✔️
 code_117 | [图像均值漂移分割](python/code_117)   | ✔️
 code_118 | [Grabcut-图像分割](python/code_118)   | ✔️
-code_119 | [Grabcut-背景替换](python/code_119)   | ✏️
+code_119 | [Grabcut-背景替换](python/code_119)   | ✏️
+code_120 | [二维码检测识别](python/code_120)   | ✔️