Log Message:
aerc: update to 0.18.1

Upstream Changes in 0.18.1:
- bug fixes

Upstream Changes in 0.18.0:
- added a variety of new commands
- inline image previews when no filter is defined for `image/*` and
  the terminal supports it
- message counts are available in statusline templates
- virtually any key binding can now be configured in binds.conf,
  including Shift+Alt+Control modifier combinations
- create notmuch named queries with the `:query` command.
- new `pgp-self-encrypt` option in `accounts.conf
- calendar responses now ignore case.
- allow account- and folder-specific binds to coexist.
- fixed crash when running `:send` with a `:preview` tab focused.
- deadlock when running `aerc mailto:foo@bar.com` without another
  instance of aerc already running.
- prevent a freeze for large-scale deletions with IMAP.
- `mime-Version` is no longer inserted in signed text parts headers
- restore previous behaviour of the new message bell

Many others updates https://git.sr.ht/~rjarry/aerc/refs/0.18.0 and
https://git.sr.ht/~rjarry/aerc/refs/0.18.1