F2 is not very portable e.g., doesn't work over putty (default settings).

In certain workflows you know you would have revisit a directory. Mark it!

^Q would quit even from filter mode

1. Open directories in filter mode
2. Fix arrow keys not working after filter selection (due to invalid cur entry)
3. Support `Insert` key to clear filter prompt
4. Update documentation

Reasons:

gnome-search-tool is much more powerful than other tools in its category. It
supports numerous search parameters like size, modification date and supports
text search.

This change remaps the & key. However, / is more relevant for filter and & makes more sense wrt. address.

Add .Ed to match with .Bd