Fixed grammatical mistake in README.md (#2260)

Fix a minor grammatical mistake in the README.md documentation file. This improves the general quality of the project.

README.md

@@ -10,7 +10,7 @@
 
 [**OpenPose**](https://github.com/CMU-Perceptual-Computing-Lab/openpose) has represented the **first real-time multi-person system to jointly detect human body, hand, facial, and foot keypoints (in total 135 keypoints) on single images**.
 
-It is **authored by** [**Ginés Hidalgo**](https://www.gineshidalgo.com), [**Zhe Cao**](https://people.eecs.berkeley.edu/~zhecao), [**Tomas Simon**](http://www.cs.cmu.edu/~tsimon), [**Shih-En Wei**](https://scholar.google.com/citations?user=sFQD3k4AAAAJ&hl=en), [**Yaadhav Raaj**](https://www.raaj.tech), [**Hanbyul Joo**](https://jhugestar.github.io), **and** [**Yaser Sheikh**](http://www.cs.cmu.edu/~yaser). It is **maintained by** [**Ginés Hidalgo**](https://www.gineshidalgo.com) **and** [**Yaadhav Raaj**](https://www.raaj.tech). OpenPose would not be possible without the [**CMU Panoptic Studio dataset**](http://domedb.perception.cs.cmu.edu). We would also like to thank all the people who [has helped OpenPose in any way](doc/09_authors_and_contributors.md).
+It is **authored by** [**Ginés Hidalgo**](https://www.gineshidalgo.com), [**Zhe Cao**](https://people.eecs.berkeley.edu/~zhecao), [**Tomas Simon**](http://www.cs.cmu.edu/~tsimon), [**Shih-En Wei**](https://scholar.google.com/citations?user=sFQD3k4AAAAJ&hl=en), [**Yaadhav Raaj**](https://www.raaj.tech), [**Hanbyul Joo**](https://jhugestar.github.io), **and** [**Yaser Sheikh**](http://www.cs.cmu.edu/~yaser). It is **maintained by** [**Ginés Hidalgo**](https://www.gineshidalgo.com) **and** [**Yaadhav Raaj**](https://www.raaj.tech). OpenPose would not be possible without the [**CMU Panoptic Studio dataset**](http://domedb.perception.cs.cmu.edu). We would also like to thank all the people who [have helped OpenPose in any way](doc/09_authors_and_contributors.md).