feat(plugins): add zbell plugin to notify when commands end (#3034)

Closes #3034

plugins/zbell/README.md

@@ -0,0 +1,30 @@
+# zbell plugin
+
+This plugin prints a bell character when a command finishes if it has been
+running for longer than a specified duration.
+
+To use it, add `zbell` to the plugins array in your zshrc file:
+
+```zsh
+plugins=(... zbell)
+```
+
+## Settings
+
+These settings need to be set in your zshrc file, before Oh My Zsh is sourced.
+
+- `zbell_duration`: duration in seconds after which to consider notifying
+  the end of a command. Default: 15 seconds.
+
+- `zbell_ignore`: if there are programs that you know run long that you
+  don't want to bell after, then add them to the `zbell_ignore` array.
+  By default, `$EDITOR` and `$PAGER` are ignored:
+
+  ```zsh
+  zbell_ignore=($EDITOR $PAGER)
+  ```
+
+## Author
+
+Adapted from an original version by [Jean-Philippe Ouellet](https://github.com/jpouellet).
+Made available under the ISC license.