Improve icon fetching by file extension

[luissimas]

This adds the support for different icons when dealing with files that have multiple extensions (like users.test.js).

The motivation for this is based on this issue from nvim-web-devicons.

Given this sample config file for nvim-web-devicons:

require("nvim-web-devicons").setup {
  override = {
    ["test.js"] = {
      icon = "ﭧ",
      color = "#cbcb41",
      name = "JsTest"
    },
    ["spec.js"] = {
      icon = "",
      color = "#cbcb41",
      name = "JsSpec"
    },
    ["test.lua"] = {
      icon = "ﭧ",
      color = "#51a0cf",
      name = "LuaTest"
    },
    ["spec.lua"] = {
      icon = "",
      color = "#51a0cf",
      name = "LuaSpec"
    }
  },
  default = true
}

Original behavior

New behavior

[kyazdani42]

this solution looks pretty good to me, i'm gonna test it out later today, and if it works as expected i'll merge it :) thanks

[kyazdani42]

looks like it works fine :) thanks for the contribution !