feat: add sheets_insert_rows tool for inserting rows with optional da…

[freema]

This pull request introduces a new feature for inserting rows into Google Sheets and improves documentation and validation for related tools. The most significant changes are the addition of the sheets_insert_rows tool, enhancements to the sheets_append_values description, and the corresponding updates to documentation and tests.

New Tool: Row Insertion

• Added new sheets_insert_rows tool to insert rows at a specific position with optional data, formatting inheritance, and flexible value input options (RAW or USER_ENTERED). Includes implementation in src/tools/insert-rows.ts, registration in src/index.ts, and export in src/tools/index.ts. [1] [2] [3] [4]
• Added input validation for sheets_insert_rows via validateInsertRowsInput in src/utils/validators.ts, ensuring correct types, defaults, and error handling for all parameters.

Documentation and Usability Improvements

• Updated README.md to document the new sheets_insert_rows tool, its parameters, and usage examples. Also clarified the default overwrite behavior of sheets_append_values and how to insert new rows. [1] [2]
• Enhanced the description of sheets_append_values in src/tools/append-values.ts to warn users about the default OVERWRITE behavior and how to use INSERT_ROWS instead.
• Updated the changelog in CHANGELOG.md to reflect new features and documentation changes for version 1.5.0.
• Bumped package version to 1.5.0 in package.json.

Testing

• Added comprehensive unit tests for the new handleInsertRows function in tests/unit/tools/insert-rows.test.ts, covering basic insertion, value population, formatting inheritance, error handling, and edge cases.
• Added and tested input validation for sheets_insert_rows in tests/unit/utils/validators.test.ts, ensuring robust error reporting and correct defaults. [1] [2]…ta and enhance validation