embedding_layer: update readme

Author: OneAdder

README.md

@@ -30,6 +30,7 @@ Read the paper [here](https://arxiv.org/abs/1902.06714).
 | Layer type | Constructor name | Supported input layers | Rank of output array | Forward pass | Backward pass |
 |------------|------------------|------------------------|----------------------|--------------|---------------|
 | Input | `input` | n/a | 1, 2, 3 | n/a | n/a |
+| Embedding | `embedding` | n/a | 2 | ✅ | ✅ |
 | Dense (fully-connected) | `dense` | `input1d`, `dense`, `dropout`, `flatten` | 1 | ✅ | ✅ |
 | Dropout | `dropout` | `dense`, `flatten`, `input1d` | 1 | ✅ | ✅ |
 | Convolutional (2-d) | `conv2d` | `input3d`, `conv2d`, `maxpool2d`, `reshape` | 3 | ✅ | ✅(*) |