Replace Bars with Heatmap in GSEA Iceberg Plots to Show Gene Saturation

[ritamtbsilva]

The current GSEA "iceberg" plots use vertical bars to represent individual gene positions and ranks. However, this design doesn't effectively convey gene saturation or density.

Proposed Improvement:

• Replace the bars with a heatmap or density strip to more accurately reflect the concentration of genes along the ranked list.
• Use color intensity to indicate gene density or saturation at each rank position.

[ritamtbsilva]

Not trivial since I am using directly fgsea::plotEnrichment(). Applying fgsea::calcGseaStat() to get the ES curve seemed to not work.