feat: add pathParamEscaped support

[alswl]

Provide a way to control path parmas.

fix #138

[youyuanwu]

#138 was marked as won't fix.
openapi v2 does not specify this behavior, so I vote down for this to be merged.
@casualjim thoughts?

[casualjim]

I think this is a risky change that allows for ambiguity in routes.

It seems that it's not supported, unless I misunderstand the discussions here which is entirely possible:
OAI/OpenAPI-Specification#892
OAI/OpenAPI-Specification#2653

This is an open issue even for the current openapi specifications, so I'm also not in favor for this change.

[alswl]

Is it possible to provide a feature gate to enable this feature. In real world, some project is using slash in the HTTP router .

[youyuanwu]

If (when) openapi decides to incorporate this feature, go-openapi can add this support. But for now, please follow up with openapi feature proposals which casualjim linked above.