Added resession extension to persist tabpage names across sessions

[hjfeldy]

This feature adds a resession.nvim extension.

To enable the extension in your resession.nvim config, simply add an entry for it in your resession configuration:

Lazy.nvim example:

-- lua/plugins/resession.lua
return {
  "stevearc/resession.nvim",
  lazy = false,
  dependencies = {
      "akinsho/bufferline.nvim",   
  },
  opts = {
    extensions = {
      bufferline = {}
    } 
  }
}

Now, when sessions are saved/loaded with resession.nvim, the bufferline tab-page names will persist.

Note: I put this together for the explicit purpose of better integrating bufferline with scope.nvim. Bufferline works out of the box with scope.nvim in almost every way. Tabpages are persisted, as are the per-tab pseudo-bufferlists that scope.nvim uses. However, even though the tabpages' content gets persisted, all of the tabs are renamed to 1,2...N whenever reloading a session. With this very small addition to bufferline, the combined usage of scope.nvim, bufferline .nvim, and resession.nvim feels very nice.