Miniflux: Allow customising the healthcheck path

[gerrowadat]

This is necessary when setting a BASE_URL that has a path component, as miniflux also shunts its /healthcheck endpoint under there.

[gabe565]

@gerrowadat Oh, thanks! Good catch. My only concern is since app-template automatically creates services for anything in the services block, it feels like this should maybe go somewhere else in values.yaml. I'll look at the upstream chart and see if there's a better fit.

[gerrowadat]

Hey, thanks for looking. Happy to put this wherever makes sense!