Add X-axis and Y-axis title/label options to Heatmap charts

What is the problem or goal you're trying to solve or accomplish?

Heatmap charts currently provide no way to add titles/labels to the X-axis or Y-axis. Other chart types in Superset/Preset expose "X Axis Title" and "Y Axis Title" customization fields, but the Heatmap chart's Customize panel only offers axis interval, margin, and formatting controls. This leaves heatmaps harder to interpret on their own, since viewers can't tell what each axis represents without external context (a dashboard markdown note, the chart title, or prior knowledge of the dataset).

How are you solving it currently?

There is no in-chart workaround. Customers are currently limited to encoding axis meaning in the chart title, adding a separate Markdown component on the dashboard, or relying on the underlying column names being self-explanatory. None of these label the axes directly on the heatmap visualization itself.

What is your recommended solution?

Add "X Axis Title" and "Y Axis Title" text input fields to the Customize tab of the Heatmap chart, consistent with how other ECharts-based chart types (e.g., Bar, Line) already expose axis title controls. Ideally include the same supporting options those charts offer, such as axis title margin/position, so the labels render cleanly alongside the existing axis tick values.