corrplot v0.90

• Add customizable rectangles to correlation plots in corrRect().(#185, requirements from @douglaswhitaker thanks).
• Remove clus; add index and name parameters in corrRect().
• Add xName, yName two columns in corrPos data frame(e.g. corrplot(...)$corrPos).
• Rename parameter cl.lim to col.lim.
• Add arg to the corrplot() return list.
• Add pipe operator |> examples when using corrRect().
• Set 'seriation' as Suggests package, and add examples in the document.
• Parameter number.digits also works on p-value. (thanks, @bassam-abulnoor)
• Revise the document. (thanks, Shuai Huang)