fix(lint): Fix linting issues (#487)

This pull request focuses on improving the documentation and readability of the Webex meme bot application by adding docstrings and minor formatting adjustments. Here's a breakdown of the changes:

*   **Docstrings:**
    *   Added module-level docstrings to `app/close.py`, `app/img.py`, and `app/main.py` providing a high-level overview of the purpose of each module.
    *   Added docstrings to classes (`ExitCommand`, `MakeMemeCommand`, `MakeMemeCallback`) describing their role.
    *   Added docstrings to methods within those classes (`__init__`, `pre_execute`, `execute`, `post_execute`) explaining their functionality, arguments, and return values where applicable. The `get_templates` and `format_meme_string` functions in `app/img.py` have been documented as well.
*   **Formatting:**
    *   Added a line break before the return type annotation in function definitions (e.g., `def execute(...) -> Response:`).
    *   Added the disable comment `# pylint: disable=line-too-long` to a line in `app/meme.py` to disable pylint for that line.
    *   Added the disable comment `# pylint: disable=unused-argument` to the `pre_execute`, `execute`, and `post_execute` methods to disable pylint checks about unused arguments. This is because these methods are part of an interface and must have the same signature even if some arguments are unused.
*   **Variable Naming:**
    *   Renamed the `vars` dictionary to `env_vars` in `tests/test_config.py` for better clarity.
*   **Test Update:**
    *   Added a docstring to the `test_config` function in `tests/test_config.py` to explain its functionality.
*   **Imports Update:**
    *   Updated imports in `tests/test_config.py` to disable pylint for wrong-import-position errors using `# pylint: disable=wrong-import-position`.

In essence, these changes enhance the maintainability and understandability of the codebase through comprehensive documentation and minor code style improvements.

Reviewed-on: #487

app/main.py

@@ -1,5 +1,7 @@
 #!/usr/local/bin/python3
 
+"""Main entry point for the Webex Bot application."""
+
 from webex_bot.webex_bot import WebexBot
 
 from app import close, meme
@@ -18,6 +20,7 @@ def create_bot() -> WebexBot:
 
 
 def main() -> None:
+    """Main function to run the Webex Bot."""
     bot: WebexBot = create_bot()
     bot.add_command(meme.MakeMemeCommand())
     bot.add_command(close.ExitCommand())