fix: reimplement the deprecated function tbl_add_reverse_lookup (#904)

lua/bufferline/diagnostics.lua

@@ -1,13 +1,14 @@
 local lazy = require("bufferline.lazy")
 local config = lazy.require("bufferline.config") ---@module "bufferline.config"
 local ui = lazy.require("bufferline.ui") ---@module "bufferline.ui"
+local utils = lazy.require("bufferline.utils") ---@module "bufferline.utils"
 
 local M = {}
 
 local fn = vim.fn
 local fmt = string.format
 
-local severity_name = vim.tbl_add_reverse_lookup({
+local severity_name = utils.tbl_add_reverse_lookup({
   [1] = "error",
   [2] = "warning",
   [3] = "info",

lua/bufferline/utils/init.lua

@@ -121,6 +121,22 @@ function M.tbl_reverse_lookup(tbl)
   return ret
 end
 
+--- creates a table containing the forward and reversed mapping from the provided
+--- table.
+--- similar to the now deprecated vim.tbl_add_reverse_lookup
+--- @generic K,V
+--- @param tbl table<K,V>
+--- @return table<V,K>
+function M.tbl_add_reverse_lookup(tbl)
+  local ret = {}
+  for k, v in pairs(tbl) do
+    ret[k] = v
+    ret[v] = k
+  end
+
+  return ret
+end
+
 M.path_sep = vim.fn.has("win32") == 1 and "\\" or "/"
 
 -- The provided api nvim_is_buf_loaded filters out all hidden buffers