Add nano and vim-tiny for usability in interactive prompt

[corneliusroemer]

Resolves #177

Image size increase should be <1MB unless some libraries are added as well (we'll see in CI):

$ du -h | grep vim
12K     ./etc/vim
4.0K    ./var/lib/vim/addons
8.0K    ./var/lib/vim
12K     ./usr/share/bug/vim-tiny
32K     ./usr/share/doc/vim-common
32K     ./usr/share/doc/vim-tiny
16K     ./usr/share/vim/vim82/doc
24K     ./usr/share/vim/vim82
28K     ./usr/share/vim

$ du -h | grep nano
4.0K    ./usr/share/doc/nano/examples
12K     ./usr/share/doc/nano
36K     ./usr/share/nano/extra
196K    ./usr/share/nano
4.0K    ./nextstrain/.local/share/nano

[tsibley]

Size difference is about 2MB.

$ docker image inspect --format '{{.Size}}' nextstrain/base:branch-add-nano-and-vim-tiny 
2056610544

$ docker image inspect --format '{{.Size}}' nextstrain/base:build-20230905T192825Z
2054525750

$ python
>>> (2056610544 - 2054525750) / 1000 / 1000
2.084794

[tsibley]

This seems fine (and the size bump is noise given what the image's bloated to), although I'd think the vast majority of folks would edit outside of nextstrain shell instead of using vim or nano inside of it.

Are you thinking we'd make a corresponding change to the Conda runtime too, or not?