Modify README compatibility matrix, and move the implemented design into Implemented directory. (#6087)

Signed-off-by: Xun Jiang <blackpiglet@gmail.com>
Co-authored-by: Xun Jiang <blackpiglet@gmail.com>

README.md

@@ -40,6 +40,7 @@ The following is a list of the supported Kubernetes versions for each Velero ver
 
 | Velero version | Expected Kubernetes version compatibility | Tested on Kubernetes version           |
 |----------------|-------------------------------------------|----------------------------------------|
+| 1.11           | 1.18-latest                               | 1.23.10, 1.24.9, 1.25.5, and 1.26.1    |
 | 1.10           | 1.18-latest                               | 1.22.5, 1.23.8, 1.24.6 and 1.25.1      |
 | 1.9            | 1.18-latest                               | 1.20.5, 1.21.2, 1.22.5, 1.23, and 1.24 |
 | 1.8            | 1.18-latest                               |                                        |