Integrate a Vim-like text editor/plugin in a new mode similar to insert mode

This was a comment in #51, but I think it deserves its own thread.

The suggestion is to add a new mode `InputfieldNormal` in input field such that entering keys does not edit the input field but moves the cursor like in vim. For e.g.,  w moves the cursor using <c-right> and b moves the cursor using <c-left> and k moves the cursor using <up> etc. And i brings back the insert mode.