Handbook: update marketing slack channels (#11895)

Updated Slack channels added "#g-website" DRI Mike Thomas

# Checklist for submitter

If some of the following don't apply, delete the relevant line.

- [ ] Changes file added for user-visible changes in `changes/` or
`orbit/changes/`.
See [Changes
files](https://fleetdm.com/docs/contributing/committing-changes#changes-files)
for more information.
- [ ] Documented any API changes (docs/Using-Fleet/REST-API.md or
docs/Contributing/API-for-contributors.md)
- [ ] Documented any permissions changes
- [ ] Input data is properly validated, `SELECT *` is avoided, SQL
injection is prevented (using placeholders for values in statements)
- [ ] Added support on fleet's osquery simulator `cmd/osquery-perf` for
new osquery data ingestion features.
- [ ] Added/updated tests
- [ ] Manual QA for all new/changed functionality
  - For Orbit and Fleet Desktop changes:
- [ ] Manual QA must be performed in the three main OSs, macOS, Windows
and Linux.
- [ ] Auto-update manual QA, from released version of component to new
version (see [tools/tuf/test](../tools/tuf/test/README.md)).

handbook/marketing/README.md

@@ -739,6 +739,7 @@ These groups maintain the following [Slack channels](https://fleetdm.com/handboo
 | Slack channel               | [DRI](https://fleetdm.com/handbook/company#group-slack-channels)    |
 |:----------------------------|:--------------------------------------------------------------------|
 | `#g-marketing`              | Jarod Reyes                                                            |
+| `#g-website`                | Mike Thomas                                                            |
 | `#fleet-mindshare-pr`       | Jarod Reyes                                                            |
 | `#help-public-relations`    | Jarod Reyes                                                            |
 | `#help-promote`             | Jarod Reyes                                                            |