route type 'local' is not supported: Error in network definition: invalid route type 'local'

[Nobuto Murata]

netplan 1.10.1-5build1 on Ubuntu bionic.

I'd like to add a route with type=local described in the two following docs:

1. sslh
https://github.com/yrutschle/sslh/blob/master/doc/config.md#transparent-proxy-support
2. tproxy in kernel
https://www.kernel.org/doc/Documentation/networking/tproxy.txt

(both docs are talking about the same thing)
> # Configure routing for those marked packets
> ip rule add fwmark 0x1 lookup 100
> ip route add local 0.0.0.0/0 dev lo table 100

However, it looks like netplan doesn't support type=local in the routes:

/etc/netplan/90-local-lo.yaml:18:17: Error in network definition: invalid route type 'local'
          type: local
                ^
https://github.com/CanonicalLtd/netplan/blob/521a69554d2c29df7e9674ec874d5a29a13b9fdd/src/parse.c#L986-L999

It would be nice if netplan supports type=local in addition to the current ones.