[Docs] Add python code style.

Pages/Documentation/CodeStyle.md

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+---
+layout: default
+title: Code Style
+parent: Documentation
+---
+
+## Buddy Compiler Code Styles
+
+### Python Code Formatting
+
+Buddy Compiler adheres to the PEP 8 style guide while following the LLVM's formatting approach.
+See the [PEP8](https://peps.python.org/pep-0008/) and [LLVM documentation](https://llvm.org/docs/CodingStandards.html#python-version-and-source-code-formatting) for details on code style and formatting.
+Here is a list of some key points:
+
+- Formatting: Use `black` and `darker` to format the code.
+
+```
+$ pip install black=='23.*' darker # install black 23.x and darker
+$ darker test.py                   # format uncommitted changes
+$ darker -r HEAD^ test.py          # also format changes from last commit
+$ black test.py                    # format entire file
+```
+
+- Indentation: Use 4 spaces per indentation level. Do not use tabs.
+
+- Maximum Line Length: Limit all lines to a maximum of 79 characters for code, and 72 for comments and docstrings.
+
+- Imports: Imports should usually be on separate lines and grouped in the following order:
+
+    - Standard library imports.
+    - Related third-party imports.
+    - Local application/library specific imports.
+    - Place a blank line between each group of imports.
+
+- Whitespace: Use whitespace around binary operators; for instance: a = b + c. Avoid extraneous whitespace.
+
+- Comments: Add docstrings in Google style for all public functions and classes.
+
+- Naming Conventions:
+
+    - Use `CamelCase` for class names.
+    - Use `snake_case` for functions, methods, and variable names.
+    - Use `UPPERCASE_WITH_UNDERSCORES` for constants.
+
+- Whitespace in Expressions and Statements: Avoid extraneous whitespace in the following situations:
+
+    - Immediately inside parentheses, brackets, or braces.
+    - Immediately before a comma, semicolon, or colon.
+    - Immediately before the open parenthesis that starts the argument list of a function call.
+    - Immediately before the open parenthesis that starts an indexing or slicing.
+
+- Module Names:
+
+    - Modules should have short, all-lowercase names.
+    - Underscores can be used in the module name if it improves readability.
+    - Python packages (directories) should also have short, all-lowercase names, but it's preferable not to use underscores.
+
+    For example:
+
+    `my_module.py` is preferred over `MyModule.py` or `mymodule.py`.
+    For a package (directory), `mypackage` is preferred over `my_package`.
+
+- Other:
+    - Use two blank lines to separate top-level function and class definitions.
+    - Use a single blank line to separate method definitions inside a class.