rest-plugin http/2 support

[fsteff]

Describe the feature

When writing a web-UI for a zenoh-based application using the router's REST-plugin, I had the issue that the browser stopped sending requests when I subscribe to may topics (via SSE). Afaik the problem seems to be that the utilized webserver only supports HTTP/1.1.

Subscribing to a topic via Long-lived (SSE) GET requests keeps a connection to the server open, but with HTTP/1.1 most browsers limit the number of simultaneous connections to 6 (overall, not even per tab!). With HTTP/2 this should no longer be a problem.

However, the utilized webserver tide does NOT support HTTP/2 (http-rs/tide#891).
As a result, the number of concurrent subscriptions is limited, additional requests (also other ones) stop working.

Since HTTP/2 support is not planned for tide (for now only receives small maintance updates, see http-rs/tide#888), please consider switching to a webserver that supports it.