Add XMRS - instant exchange

[xmrs-swap]

Privacy-focused instant exchange with no registration, fixed and floating rates, 0% exchange fee on supported pairs, and support for 1,000+ cryptocurrencies across multiple networks.

Summary

Adds XMRS to the Crypto Exchanges section.

Checklist

• Entry uses the format [XMRS](https://xmrs.io/)
• New section is added to the Table of Contents (Contents) - N/A, added to an existing subsection
• Project has a clear privacy / own-your-data policy - https://xmrs.io/privacy-policy
• [х] Project website loads no third-party trackers (only analytics from the Analytics section allowed)
• [-] Source or repo link is provided — closed-source, no public repo
• [-] License is stated — closed-source
• Project is maintained