Updating to serde-yaml 0.9

[plugwash]

Hi, I am currently trying to update the package of the serde-yaml crate in Debian.
to 0.9.x I tried bumping the dependency in the treediff crate but the build fails with

   error[E0004]: non-exhaustive patterns: `serde_yaml::Value::Tagged(_)` not covered
      --> src/value/serde_yaml.rs:14:15
       |
    14 |         match *self {
       |               ^^^^^ pattern `serde_yaml::Value::Tagged(_)` not covered
       |

I would appreciate it if you can take a look and determine an appropriate way to handle
the new enum variant.

[Byron]

Thanks for reporting.

Unfortunately I have to declare this library to be in maintenance mode so all fixes and improvements have to be contributed. Right now, I really don't have time nor motivation, as none of my crates still use this library.

It looks like the main consumer of this library is json-patch, and I suggest to open an issue them so they contribute a fix, take over this crate, or cut the dependency to this crate in some other way.

Thanks for your help.