This makes it be enable to do this.
```bash
$ nvim --headless +'=require("frecency").query { limit = 3, json = true }' +q | jq .
[
"/path/to/most/opened/file",
"/path/to/second/file",
"/path/to/third/file"
]
```
* chore: add `debug_timer` option to log in timer
* fix: wait synchronously for DB not in coroutine
* feat: add `json` option to dump JSON for DB
* chore: track setup() time
* feat: avoid setup() to be called twice
* chore: track time between Database:start()
* feat: add bootstrap option to load DB in advance
* feat: initialize DB before frecency class starts
* chore: add more logging
* feat!: load DB in Neovim starting
only if the plugin is loaded non-lazily.
* fix: simplify logic for timer
* fix: detect error and safely finish
* chore: remove unnecessary method
* refactor: simplify logic to load web_devicons
* refactor: make register() asynchronous
* fix: load lazily modules outside this plugin
* refactor: simplify logic to wait initialization
* refactor: use uv.hrtime() instead of os.clock()
* fix: avoid errors in calling plenary.log in async
* test: store elapsed time to check in tests
* test: fix module names
This becomes a problem only in Ubuntu because macOS and Windows does not
care cases in filenames.
* test: fix types and unused modules
* style: fix by stylua
* refactor: make recency / entry_maker loaded lazily
