v0.12.0

• Added new LDResults class:
  • Stores pairwise LD statistics and analysis parameters from
    linkageDiseq()
• Added new LDRegion class:
  • Defines genomic regions for highlighting LD blocks on plotLD() plots
• Added new function plotLD():
  • Replaces deprecated ldPlot() with a redesigned LD heatmap
  • Supports Haploview and viridis-family color schemes
  • LD block highlighting via LDRegion objects
  • Optional genomic position track above the heatmap
  • Toggleable site index labels along the diagonal
• Added new function plotSnpDensity():
  • Generates heatmap-style SNP density plots across chromosomes
  • Configurable window size, viridis color palettes, and log-scaled counts
• Removed deprecated ldPlot() and ldJavaApp() functions
• Removed deprecated interactive Java visualizations section from vignette
• Updated vignette with new LD and SNP density visualization sections