feat(messletters): add bubble_num function

lua/spacevim/api/messletters.lua

@@ -0,0 +1,30 @@
+--=============================================================================
+-- messletters.lua --- messletters api
+-- Copyright (c) 2016-2019 Wang Shidong & Contributors
+-- Author: Wang Shidong < wsdjeg@outlook.com >
+-- URL: https://spacevim.org
+-- License: GPLv3
+--=============================================================================
+
+
+local M = {}
+
+
+function M.bubble_num(num, t)
+    local list = {}
+
+    table.insert(list, {'➊', '➋', '➌', '➍', '➎', '➏', '➐', '➑', '➒', '➓'})
+    table.insert(list, {'➀', '➁', '➂', '➃', '➄', '➅', '➆', '➇', '➈', '➉'})
+    table.insert(list, {'⓵', '⓶', '⓷', '⓸', '⓹', '⓺', '⓻', '⓼', '⓽', '⓾'})
+
+    local n = ''
+
+    pcall(function ()
+        n = list[t + 1][num]
+    end)
+
+    return n
+end
+
+
+return M