fix: remove trailing slash to allow deparam with urls that end with a slash

[m-thompson-code]

Description

I'm working with a team to perform static site generation that works with can-route, and currently, can-route's canRoute_deparam method doesn't handle urls that end with a trailing slash (/) properly. This has become problematic when trying to use express to act as a local static server during development.

This PR updates canRoute_deparam to removing trailing slash (/) from url when trying to deparam for path variables.

Recreate Steps

import route from "can-route"
import "can-stache-route-helpers"

route.urlData = new RoutePushstate()

route.register("{page}", { page: "home" })
route.register("tasks/{taskId}", { page: "tasks" })
route.register("progressive-loading/{loadId}", { page: "progressive-loading" })

route.start()

This allows for urls like: "progressive-loading/moo" which deparams to:

{
  "page": "progressive-loading",
  "loadId": "moo"
}

When the url is: "progressive-loading/moo/" (has trailing slash /), deparams to empty object:

{}

When removing the trailing slash (/) then attempting to deparam works as expected.

Reason to support urls with trailing slash (/)

When serving static pages using express, following their basic static server example looks something like this:

const express = require("express")
const app = express()

app.use(express.static('static_files'))// return all static files from "static_files"
app.use("*", express.static('static_files/404'))// if there's no match, return 404 page

app.listen(8080, function () {
  console.log("Example app listening on port 8080")
})

"/static_files/":

/static_files/index.html
/static_files/tasks/index.html
/static_files/progressive-loading/root/index.html
/static_files/progressive-loading/moo/index.html
/static_files/progressive-loading/cow/index.html
/static_files/404/index.html

[m-thompson-code]

A workaround to this is to provide doubles for each register:

route.register("{page}", { page: "home" })
route.register("{page}/", { page: "home" })
route.register("tasks/{taskId}", { page: "tasks" })
route.register("tasks/{taskId}/", { page: "tasks" })
route.register("progressive-loading/{loadId}", { page: "progressive-loading" })
route.register("progressive-loading/{loadId}/", { page: "progressive-loading" })

thanks @bmomberger-bitovi for your suggestion

[m-thompson-code]

Something that is missing from this PR is the ability to generate urls given a trailing /:

for example { page: 'first', action: 'second'} should be able to generate a url "/first/second/" instead of "/first/second"

To avoid breaking changes, this PR should instead add an option to switch into defaulting into this behavior