add version 3.16.3 to /releases page

[klandergren]

As of today (2025 Fri May 23), it appears:

• /releases shows 3.16.1 as the latest release
• 3.16.3 was cut in the most recent commit

I haven't looked into why /releases is out of date but think it should be updated.

context: I am resolving peer dependency warnings related to react 19 upgrade and went to /releases only to see that the version I had (3.16.1) was seemingly the latest. Only after looking at commits did I see that others were available.

p.s. Thank you for react-modal!