Add Kubernetes anniversary as an annual event on the community calendar

# Kubernetes Anniversary Calendar Event

The Kubernetes anniversary ([first commit](https://github.com/kubernetes/kubernetes/commit/2c4b3a562ce34cddc3f8218a2c4d11c7310e6d56/) and public announcement, June 6, 2014) is not on `calendar@kubernetes.io`, and I think this is something worth sharing in the [community calendar](https://www.kubernetes.dev/resources/calendar/) so we don't miss it.

## Proposal

Add a recurring all-day event to `calendar@kubernetes.io`:

| Field | Value |
|---|---|
| **Title** | Kubernetes Anniversary 🎂 |
| **Date** | June 6, all-day, repeats yearly |
| **Visibility** | Public |
| **Description** | Kubernetes was announced and its first commit landed on June 6, 2014.

`/sig contributor-experience`
`/area contributor-comms`

cc @kaslin @mfahlandt @palnabarun @MadhavJivrajani @Priyankasaggu11929

Start with the community calendar at https://www.kubernetes.dev/resources/calendar/ and the calendar@kubernetes.io contribution process. Add the public recurring all-day event with the specified title, June 6 date, yearly recurrence, and description; done means the Kubernetes anniversary appears correctly on the community calendar.

Written by the indexing model from the issue text.