Escape file name for file to edit

Use `fnameescape` before trying to edit a file when you open it through
a link.

lua/test/action_spec.lua

@@ -1,7 +1,12 @@
 local action = require 'zettelkasten.action'
 
 before_each(function()
-    _G.vim = {g = {}, b = {}, loop = {fs_scandir = function() end}}
+    _G.vim = {
+        g = {},
+        b = {},
+        fn = {fnameescape = function(input) return input end},
+        loop = {fs_scandir = function() end}
+    }
 end)
 after_each(function() _G.vim = nil end)
 

lua/zettelkasten/action.lua

@@ -11,7 +11,7 @@ function A.open(link)
     if not link or not link.ref then return end
     local fname = f.get_zettel_by_anchor(link.anchor) or
                       f.get_zettel_by_ref(link.ref) or link.ref
-    vim.api.nvim_command(string.format("edit %s", fname))
+    vim.api.nvim_command(string.format("edit %s", vim.fn.fnameescape(fname)))
 end
 
 -- Gets the input at the current buffer cursor and opens it