Add chart functionality to gspread

[darkfiberiru]

This commit adds comprehensive chart support to gspread, enabling users to create, update, delete, and list charts in Google Sheets.

New features:

• Worksheet.add_chart() - Create charts with customizable properties
• Worksheet.update_chart() - Modify existing chart specifications
• Worksheet.delete_chart() - Remove charts by ID
• Worksheet.list_charts() - List all charts in a worksheet

New enums in utils:

• ChartType - Chart types (column, line, area, bar, scatter, combo, stepped_area)
• ChartLegendPosition - Legend positions (bottom, left, right, top, no_legend)
• ChartAxisPosition - Axis positions (bottom_axis, left_axis, right_axis)

Implementation details:

• Uses Google Sheets API v4 batchUpdate endpoint
• Supports multiple data series per chart
• Handles both single-range (auto-generated domain) and multi-range (explicit domain) data
• Includes input validation for data ranges and dimensions
• Converts A1 notation to GridRange format
• Properly handles enum to string conversion for API calls

Documentation:

• Added comprehensive user guide section with examples
• Includes usage examples for all chart operations
• Documents all chart types and configuration options

Fixes applied during code review:

• Fixed enum string conversion for ChartAxisPosition
• Corrected data range logic for single vs multiple ranges
• Added KeyError protection in list_charts()
• Added input validation for empty ranges and invalid dimensions
• Validated non-empty series before chart creation

🤖 Generated with Claude Code

[darkfiberiru]

@burnash I understand if you not a fan of AI for personal reason or more complicated one but realizing gap in lack of ability to create graphs with gspread library I added them with help of claude-code from anthropic. So here it is.

[darkfiberiru]

I see this repo is in freeze due to lack of maintainer

[alifeee]

I see this repo is in freeze due to lack of maintainer

hi :] thanks for the suggestion. yes it is.

please see #1570

[brianjmurrell]

@darkfiberiru Something is unclear about updating an existing chart. Let's say I have this chart data range currently defined:

How do I extend the data range, axis and series down to say line 575? I didn't see anything in Worksheet.update_chart() to update those.