docs: Add "Improve Component" tool documentation and update related guides

docs/docs/tools/improve_component.md

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+## Overview
+The `improve_component` tool generates code suggestions for a specific code component that changed in the PR.
+it can be invoked manually by commenting on any PR:
+```
+/improve_component component_name
+```
+
+To get a list of the components that changed in the PR and choose the relevant component interactively, use the [`analyze`](./analyze.md) tool.
+
+
+Example result:
+
+![improve_component1](https://codium.ai/images/pr_agent/improve_component1.png){width=768}
+
+![improve_component2](https://codium.ai/images/pr_agent/improve_component2.png){width=768}
+
+**Notes**
+- Language that are currently supported by the tool: Python, Java, C++, JavaScript, TypeScript.
+
+## Configuration options
+- `num_code_suggestions`: number of code suggestions to provide. Default is 4
+- `extra_instructions`: Optional extra instructions to the tool. For example: "focus on ...".
+- `file`: in case there are several components with the same name, you can specify the relevant file.
+- `class_name`: in case there are several methods with the same name in the same file, you can specify the relevant class name.