Minor refactor (#57)

- [x] Define OPTIONS as global in opts::eval
- [x] Add script
- [x] Minor changes

scripts/docker

@@ -0,0 +1,21 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+debian="${1:-false}"
+
+if $debian; then
+   docker run \
+      -it \
+      --entrypoint /bin/bash \
+      -v "$(pwd):/navi" \
+      debian \
+      -c 'apt update; apt install -y git curl; git clone --depth 1 https://github.com/junegunn/fzf.git ~/.fzf && yes | ~/.fzf/install; export PATH=$PATH:/navi; bash'
+else
+   docker run \
+      -it \
+      --entrypoint /bin/bash \
+      -v "$(pwd):/navi" \
+      ellerbrock/alpine-bash-git \
+      -c 'git clone --depth 1 https://github.com/junegunn/fzf.git ~/.fzf && yes | ~/.fzf/install; export PATH=$PATH:/navi; bash'
+fi
+