Add mapping to table of add file/folder plus note about default mapping

[benfrain]

Updated the table to include the default mapping for adding a file/folder.
Also tweaked the text a litte to point out there is no default set for Move.

[fdschmidt93]

Many thanks :)

I'm afraid it conflicts a bit with https://github.com/nvim-telescope/telescope-file-browser.nvim/pull/6/files where I already address some of these things -- so I plan on incorporating this PR one way or another soon enough.

At the same time I need to properly test nvim-telescope/telescope.nvim#1473 before I want to settle on mappings (and how they are set by default here in telescope-file-browser).

I'll most likely be will be keeping telescope involvement at a bare minimum practically speaking up until end of February (full force on work til end of this year + travelling almost entire January, if pandemic still/will/... allows it).

[benfrain]

Yes. No worries 👍