Rename list module to files module

Renamed to 'files.lua' since it is the only module actively working on
the underlying filesystem so far -- gathering existing files and zettel
in the directories.

lua/zettelkasten/action.lua

@@ -2,7 +2,7 @@ local A = {}
 
 local o = require 'zettelkasten.options'
 local link = require 'zettelkasten.link'
-local list = require 'zettelkasten.list'
+local list = require 'zettelkasten.files'
 
 local BIGNUMBER = 10000000
 

lua/zettelkasten/action_spec.lua

@@ -19,7 +19,7 @@ describe("open", function()
     end)
     it("should use the anchor to open the corresponding zettel", function()
         vim.api = {nvim_command = mock(function() end)}
-        local ls = stub(require 'zettelkasten.list', "get_zettel")
+        local ls = stub(require 'zettelkasten.files', "get_zettel")
 
         action.open({
             ref = "1910271456_link-to-my-file.md",

lua/zettelkasten/files_spec.lua

@@ -1,4 +1,4 @@
-local ls = require 'zettelkasten.list'
+local ls = require 'zettelkasten.files'
 -- these tests, I suppose, only work on unix due to the file structure
 
 local function simple_api_mock(files)

lua/zettelkasten/init.lua

@@ -1,6 +1,6 @@
 local ZK = {}
 
-local ls = require 'zettelkasten.list'
+local ls = require 'zettelkasten.files'
 local o = require 'zettelkasten.options'
 local anchor = require 'zettelkasten.anchor'
 local action = require 'zettelkasten.action'