Fixes image type, adds document type for ChatBedrockConverse (#143)

## Description
This PR fixes the image type supported by Bedrock Anthropic and other
models. It also adds a new type for supporting documents.

### Image sample code
```python
from langchain_core.messages import HumanMessage
from langchain_aws import ChatBedrock

llm = ChatBedrock(
    model_id="anthropic.claude-3-sonnet-20240229-v1:0",
    beta_use_converse_api=True
)

# Convert image to bytes
image_path = "images/random-image.jpg"
image_bytes = None
with open(image_path, "rb") as f:
    image_bytes = f.read()

messages = [
    HumanMessage(
        content=[
            {
                "type": "image",
                "image": {
                    "format": "jpeg",
                    "source": {
                        "bytes": image_bytes
                    }
                }
            },
            "What is this image about?"
        ]
    )
]

llm.invoke(messages)
```

### Document sample code
```python
from langchain_core.messages import HumanMessage
from langchain_aws import ChatBedrock

llm = ChatBedrock(
    model_id="anthropic.claude-3-sonnet-20240229-v1:0",
    beta_use_converse_api=True
)

# Convert document to bytes
doc_path = "documents/random-doc.pdf"
doc_bytes = None
with open(doc_path, "rb") as f:
    doc_bytes = f.read()

messages = [
    HumanMessage(
        content=[
            {
                "type": "document",
                "document": {
                    "format": "pdf",
                    "name": "random-doc",
                    "source": {
                        "bytes": doc_bytes
                    }
                }
            },
            "What is this document about?"
        ]
    )
]

llm.invoke(messages)
```



Related to #75
Fixes #132

libs/aws/langchain_aws/chat_models/bedrock_converse.py

@@ -622,7 +622,7 @@ def _messages_to_bedrock(
         if isinstance(msg, HumanMessage):
             # If there's a human, tool, human message sequence, the
             # tool message will be merged with the first human message, so the second
-            # human message will now be preceeded by a human message and should also
+            # human message will now be preceded by a human message and should also
             # be merged with it.
             if bedrock_messages and bedrock_messages[-1]["role"] == "user":
                 bedrock_messages[-1]["content"].extend(content)
@@ -747,7 +747,7 @@ def _anthropic_to_bedrock(
         elif block["type"] == "image":
             # Assume block is already in bedrock format.
             if "image" in block:
-                bedrock_content.append(block)
+                bedrock_content.append({"image": block["image"]})
             else:
                 bedrock_content.append(
                     {
@@ -764,6 +764,9 @@ def _anthropic_to_bedrock(
             bedrock_content.append(
                 {"image": _format_openai_image_url(block["imageUrl"]["url"])}
             )
+        elif block["type"] == "document":
+            # Assume block in bedrock document format
+            bedrock_content.append({"document": block["document"]})
         elif block["type"] == "tool_use":
             bedrock_content.append(
                 {

libs/aws/tests/unit_tests/chat_models/test_bedrock_converse.py

@@ -161,6 +161,26 @@ def test__messages_to_bedrock() -> None:
                 {"type": "guard_content", "text": "hu6"},
             ]
         ),
+        HumanMessage(
+            content=[
+                {
+                    "type": "document",
+                    "document": {
+                        "format": "pdf",
+                        "name": "doc1",
+                        "source": {"bytes": b"doc1_data"},
+                    },
+                }
+            ]
+        ),
+        HumanMessage(
+            content=[
+                {
+                    "type": "image",
+                    "image": {"format": "jpeg", "source": {"bytes": b"image_data"}},
+                }
+            ]
+        ),
     ]
     expected_messages = [
         {"role": "user", "content": [{"text": "hu1"}, {"text": "hu2"}]},
@@ -229,6 +249,14 @@ def test__messages_to_bedrock() -> None:
                 },
                 {"guardContent": {"text": {"text": "hu5"}}},
                 {"guardContent": {"text": {"text": "hu6"}}},
+                {
+                    "document": {
+                        "format": "pdf",
+                        "name": "doc1",
+                        "source": {"bytes": b"doc1_data"},
+                    }
+                },
+                {"image": {"format": "jpeg", "source": {"bytes": b"image_data"}}},
             ],
         },
     ]