bug#61726: [PATCH] Eglot: Support positionEncoding capability

[Eli Zaretskii]

> From: Augusto Stoffel <arstoffel@gmail.com>
> Cc: joaotavora@gmail.com,  61726@debbugs.gnu.org
> Date: Fri, 24 Feb 2023 17:39:11 +0100
> 
> If someone thinks this is a good and useful feature, of course they
> could work on it.  I think the current behavior (json-serialize error)
> is better because it sticks to the letter of the specs.

The spec doesn't tell us to signal an error, it tells us not to send
invalid UTF-8.  Which under my proposal we will still adhere to.