feat(plugins): Add new isodate plugin for friendly date formatting commands (#9963)

* add isodate plugin

plugins/isodate/README.md

+# Isodate plugin
+
+**Maintainer:** [@Frani](https://github.com/frani)
+
+This plugin adds completion for the [ISO 8601](https://en.wikipedia.org/wiki/ISO_8601),
+as well as some aliases for common Date commands.
+
+To use it, add `isodate` to the plugins array in your zshrc file:
+
+```zsh
+plugins=(... isodate)
+```
+
+## Aliases
+
+| Alias         | Command                              | Description                                                                |
+|---------------|--------------------------------------|----------------------------------------------------------------------------|
+| isodate       | `date +%Y-%m-%dT%H:%M:%S%z`          | Display the current date with UTC offset and ISO 8601-2 extended format    |
+| isodate_utc   | `date -u +%Y-%m-%dT%H:%M:%SZ`        | Display the current date in UTC and ISO 8601-2 extended format             |
+| isodate_basic | `date -u +%Y%m%dT%H%M%SZ`            | Display the current date in UTC and ISO 8601 basic format                  |
+| unixstamp     | `date +%s`                           | Display the current date as a Unix timestamp (seconds since the Unix epoch)|
+| date_locale   | `date +"%c"`                         | Display the current date using the default locale's format                 |

plugins/isodate/isodate.plugin.zsh

+# work with date ISO 8601 easy
+
+alias isodate="date +%Y-%m-%dT%H:%M:%S%z"
+alias isodate_utc="date -u +%Y-%m-%dT%H:%M:%SZ"
+alias isodate_basic="date -u +%Y%m%dT%H%M%SZ"
+alias unixstamp="date +%s"
+alias date_locale="date +"%c""