docs: Correcting some grammatical errors of README.md (#1911)

* Update README.md

Corrected some sentences grammatically.

* Update README.md
Co-authored-by: NIlkka Seppälä <iluwatar@users.noreply.github.com>

* Update README.md
Co-authored-by: NIlkka Seppälä <iluwatar@users.noreply.github.com>

README.md

@@ -21,7 +21,7 @@ Read in different language : [**zh**](localization/zh/README.md), [**ko**](local
 
 # Introduction
 
-Design patterns are the best formalized practices a programmer can use to
+Design patterns are the best, formalized practices a programmer can use to
 solve common problems when designing an application or system.
 
 Design patterns can speed up the development process by providing tested, proven
@@ -34,11 +34,11 @@ are familiar with the patterns.
 # Getting started
 
 This site showcases Java Design Patterns. The solutions have been developed by
-experienced programmers and architects from the open source community. The
-patterns can be browsed by their high level descriptions or by looking at their
-source code. The source code examples are well commented and can be thought as
+experienced programmers and architects from the open-source community. The
+patterns can be browsed by their high-level descriptions or by looking at their
+source code. The source code examples are well commented and can be thought of as
 programming tutorials on how to implement a specific pattern. We use the most
-popular battle-proven open source Java technologies.
+popular battle-proven open-source Java technologies.
 
 Before you dive into the material, you should be familiar with various
 [Software Design Principles](https://java-design-patterns.com/principles/).
@@ -56,8 +56,8 @@ of the following approaches
  - Using tags such as `Performance`, `Gang of Four` or `Data access`.
  - Using pattern categories, `Creational`, `Behavioral`, and others.
 
-Hopefully you find the object oriented solutions presented on this site useful
-in your architectures and have as much fun learning them as we had developing them.
+Hopefully, you find the object-oriented solutions presented on this site useful
+in your architectures and have as much fun learning them as we had while developing them.
 
 # How to contribute