nvim: add get_hl_hex()

.config/nvim/lua/my/functions.lua

@@ -93,4 +93,17 @@ function M.shell_capture(command)
     return result
 end
 
+-- return colours from highlight groups in web notation (#rrggbb)
+function M.get_hl_hex(hl_group)
+    local hl = vim.api.nvim_get_hl_by_name(hl_group, true)
+    local hl_hex = {}
+    if hl.foreground then
+        hl_hex.foreground = string.format('#%.6x', hl.foreground)
+    end
+    if hl.background then
+        hl_hex.background = string.format('#%.6x', hl.background)
+    end
+    return hl_hex
+end
+
 return M