title: How to make color border in ComplexHeatmap package
body: <p>In ComplexHeatmap package I can't find a way to draw a border around the heatmap. I have illustrated the question in the attached image. Can anyone please help me to do so? Thanks in advance!</p>
  
  <p>Example code:</p>
  
  <pre><code>library(ComplexHeatmap)
  library(circlize)
  
  set.seed(123)
  mat = matrix(rnorm(80, 2), 8, 10)
  mat = rbind(mat, matrix(rnorm(40, -2), 4, 10))
  rownames(mat) = paste0("R", 1:12)
  colnames(mat) = paste0("C", 1:10)
  #plot
  Heatmap(mat, cluster_rows = F, cluster_columns = F, show_heatmap_legend = FALSE)
  </code></pre>
  
  <p>Example picture with border.
  <a href="https://i.stack.imgur.com/Cwrr5.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/Cwrr5.png" alt="enter image description here"></a></p>