refact(files): create fileutils

lua/telekasten/utils/files.lua

@@ -0,0 +1,17 @@
+local M = {}
+
+function M.file_exists(fname)
+    if fname == nil then
+        return false
+    end
+
+    local f = io.open(fname, "r")
+    if f ~= nil then
+        io.close(f)
+        return true
+    else
+        return false
+    end
+end
+
+return M