Add sponsor button to main Zed repo (#46807)

Adds a Github Sponsor button to the main Zed repo

Release Notes:

- N/A

README.md

@@ -36,3 +36,11 @@ We use [`cargo-about`](https://github.com/EmbarkStudios/cargo-about) to automati
 - Is it showing a `no license specified` error for a crate you've created? If so, add `publish = false` under `[package]` in your crate's Cargo.toml.
 - Is the error `failed to satisfy license requirements` for a dependency? If so, first determine what license the project has and whether this system is sufficient to comply with this license's requirements. If you're unsure, ask a lawyer. Once you've verified that this system is acceptable add the license's SPDX identifier to the `accepted` array in `script/licenses/zed-licenses.toml`.
 - Is `cargo-about` unable to find the license for a dependency? If so, add a clarification field at the end of `script/licenses/zed-licenses.toml`, as specified in the [cargo-about book](https://embarkstudios.github.io/cargo-about/cli/generate/config.html#crate-configuration).
+
+## Sponsorship
+
+Zed is developed by **Zed Industries, Inc.**, a for-profit company.
+
+If you’d like to financially support the project, you can do so via GitHub Sponsors.
+Sponsorships go directly to Zed Industries and are used as general company revenue.
+There are no perks or entitlements associated with sponsorship.