[skip-cii] Add pyodide update instructions to HOW_TO_RELEASE (#7449)

* Add pyodide update instructions to HOW_TO_RELEASE

* [skip-ci] Update HOW_TO_RELEASE.md

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

Author: dcherian

HOW_TO_RELEASE.md

@@ -92,7 +92,15 @@ upstream        https://github.com/pydata/xarray (push)
       ```
     You're done pushing to main!
 
-13. Issue the release announcement to mailing lists & Twitter. For bug fix releases, I
+13. Update the version available on pyodide:
+    - Open the PyPI page for [Xarray downloads](https://pypi.org/project/xarray/#files)
+    - Clone the [pyodide repository](https://github.com/pyodide/pyodide).
+    - Edit `packages/xarray/meta.yaml` to update the
+        - link to the wheel (under "Built Distribution" on the PyPI page)
+        - SHA256 hash (Click "Show Hashes" next to the link to the wheel)
+    - Open a pull request to pyodide
+
+14. Issue the release announcement to mailing lists & Twitter. For bug fix releases, I
     usually only email [email protected]. For major/feature releases, I will email a broader
     list (no more than once every 3-6 months):
       - [email protected]