add check mark for gkr in readme

Author: nicole-graus

README.md

@@ -113,7 +113,7 @@ List of symbols:
 | **SNARKs** | **Lambdaworks**    | **Arkworks**       | **Halo2** | **gnark**          | **Constantine** |
 | Groth16    | :heavy_check_mark: | :heavy_check_mark: | :x:       | :heavy_check_mark: | :x:             |
 | Plonk      | 🏗️                 | :heavy_check_mark: | ✔️         | :heavy_check_mark: | :x:             |
-| GKR        | :x:                | :heavy_check_mark: | :x:       | :heavy_check_mark: | :x:             |
+| GKR        | :heavy_check_mark: | :heavy_check_mark: | :x:       | :heavy_check_mark: | :x:             |
 | **Polynomial Commitment Schemes** | **Lambdaworks**    | **Arkworks**       | **Halo2**          | **gnark**          | **Constantine** |
 | KZG10                             | :heavy_check_mark: | ✔️                  | :heavy_check_mark: | :heavy_check_mark: | :heavy_check_mark:             |
 | FRI                               | 🏗️                 | :x:                | :x:                | :heavy_check_mark: | :x:             |