Update versions and README after 0.3 release

Author: NicolasHug

README.md

@@ -136,6 +136,7 @@ The following table indicates the compatibility between versions of
 | `torchcodec`       | `torch`            | Python              |
 | ------------------ | ------------------ | ------------------- |
 | `main` / `nightly` | `main` / `nightly` | `>=3.9`, `<=3.13`   |
+| `0.3`              | `2.7`              | `>=3.9`, `<=3.13`   |
 | `0.2`              | `2.6`              | `>=3.9`, `<=3.13`   |
 | `0.1`              | `2.5`              | `>=3.9`, `<=3.12`   |
 | `0.0.3`            | `2.4`              | `>=3.8`, `<=3.12`   |

version.txt

@@ -1 +1 @@
-0.3.0a0
+0.4.0a0