Add/update the quantized ONNX model files and README.md for Transformers.js v3

## Applied Quantizations

### ❌ Based on `encoder_model.onnx` *with* slimming

```
None
```
↳ ❌ `int8`: `encoder_model_int8.onnx` (added but JS-based E2E test failed)
```
dtype not specified for "decoder_model_merged". Using the default dtype (fp32) for this device (cpu).
/home/ubuntu/src/tjsmigration/node_modules/.pnpm/[email protected]/node_modules/onnxruntime-node/dist/backend.js:25
__classPrivateFieldGet(this, _OnnxruntimeSessionHandler_inferenceSession, "f").loadModel(pathOrBuffer, options);
^

Error: Could not find an implementation for ConvInteger(10) node with name '/conv1/Conv_quant'
at new OnnxruntimeSessionHandler (/home/ubuntu/src/tjsmigration/node_modules/.pnpm/[email protected]/node_modules/onnxruntime-node/dist/backend.js:25:92)
at Immediate.<anonymous> (/home/ubuntu/src/tjsmigration/node_modules/.pnpm/[email protected]/node_modules/onnxruntime-node/dist/backend.js:67:29)
at process.processImmediate (node:internal/timers:485:21)

Node.js v22.16.0
```

### ❌ Based on `decoder_model_merged.onnx` *with* slimming

```
0%| | 0/1 [00:00<?, ?it/s]
Processing /tmp/tmpbrxdrw6t/decoder_model_merged.onnx: 0%| | 0/1 [00:00<?, ?it/s]

0%| | 0/7 [00:00<?, ?it/s]

- Quantizing to fp16: 0%| | 0/7 [00:00<?, ?it/s]/home/ubuntu/src/tjsmigration/transformers.js/scripts/float16.py:85: UserWarning: the float32 number -3.4028234663852886e+38 will be truncated to -10000.0
warnings.warn(

- Quantizing to fp16: 0%| | 0/7 [00:00<?, ?it/s]

Processing /tmp/tmpbrxdrw6t/decoder_model_merged.onnx: 0%| | 0/1 [00:00<?, ?it/s]
Traceback (most recent call last):
File "<frozen runpy>", line 198, in _run_module_as_main
File "<frozen runpy>", line 88, in _run_code
File "/home/ubuntu/src/tjsmigration/transformers.js/scripts/quantize.py", line 377, in <module>
main()
File "/home/ubuntu/src/tjsmigration/transformers.js/scripts/quantize.py", line 374, in main
quantize(input_folder, output_folder, quantization_args)
File "/home/ubuntu/src/tjsmigration/transformers.js/scripts/quantize.py", line 309, in quantize
quantize_fp16(
File "/home/ubuntu/src/tjsmigration/transformers.js/scripts/quantize.py", line 223, in quantize_fp16
check_and_save_model(model_fp16, save_path)
File "/home/ubuntu/src/tjsmigration/transformers.js/scripts/utils.py", line 29, in check_and_save_model
strict_check_model(model)
File "/home/ubuntu/src/tjsmigration/transformers.js/scripts/utils.py", line 21, in strict_check_model
raise e
File "/home/ubuntu/src/tjsmigration/transformers.js/scripts/utils.py", line 16, in strict_check_model
onnx.checker.check_model(model_or_path, full_check=True)
File "/home/ubuntu/.cache/uv/archive-v0/cQ6A7vyzEBQhtbSuz6CnD/lib/python3.12/site-packages/onnx/checker.py", line 179, in check_model
C.check_model(
onnx.onnx_cpp2py_export.shape_inference.InferenceError: [ShapeInferenceError] Inference error(s): (op_type:If, node name: optimum::if): [ShapeInferenceError] Inference error(s): (op_type:Add, node name: /model/decoder/embed_positions/Add): [ShapeInferenceError] Inferred shape and existing shape differ in rank: (1) vs (0)
```

### ✅ Based on `decoder_model_merged.onnx` *without* slimming

↳ ✅ `fp16`: `decoder_model_merged_fp16.onnx` (added)
↳ ✅ `q8`: `decoder_model_merged_quantized.onnx` (added)
↳ ✅ `int8`: `decoder_model_merged_int8.onnx` (added)
↳ ✅ `uint8`: `decoder_model_merged_uint8.onnx` (added)
↳ ✅ `q4`: `decoder_model_merged_q4.onnx` (added)
↳ ✅ `q4f16`: `decoder_model_merged_q4f16.onnx` (added)
↳ ✅ `bnb4`: `decoder_model_merged_bnb4.onnx` (added)

onnx/decoder_model_merged_bnb4.onnx

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:609a80e89b0656b8aa69dccb1f329d2ed8a88991291d22fba2e1e0e2a1e5fac5
+size 3487900

onnx/decoder_model_merged_fp16.onnx

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:7b76178a72e4998d8ba073d975b0f0261cab2332041814718bcec105bed9ac6c
+size 1925273

onnx/decoder_model_merged_int8.onnx

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:bdfc4c50af6690023dee0abff6deb9a14255351a25a697d3238eaec91d46686f
+size 1082333

onnx/decoder_model_merged_q4.onnx

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:ac57652319cae025be6b408a822c9d8f53c36d5e2dad5f9a94a5970bac2a3865
+size 3507591

onnx/decoder_model_merged_q4f16.onnx

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:f3ee37396835c8606d0a5aa1f780bb348316da284e33279a51391725cf9df033
+size 1864427

onnx/decoder_model_merged_quantized.onnx

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:bdfc4c50af6690023dee0abff6deb9a14255351a25a697d3238eaec91d46686f
+size 1082333

onnx/decoder_model_merged_uint8.onnx

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:ebadd9b1a9d6006ab0bec3b9580f8e1238787c4ed5a92452c34e7dda298c338e
+size 1082337