BREAKING: add firefox support

[ebebbington]

Fixes #24

Summary

• To support firefox, the API has been changed slightly, this makes both chrome and firefox classes maintainable. Tests have been adjusted for this and it was pretty quick and easy to do luckily
• API's for firefox and chrome client are exactly the same
• Requires a new permission: --allow-write if using firefox. example: deno run --allow-read=$TMPDIR app_test.ts
• Options can be passed to the build method, to customise the client
• The API is now as follows:

import { buildFor } from  "https://deno.land/x/sinco/mod.ts"

const Sinco = await buildFor("chrome", ...opts) // or replace "chrome" with "firefox"
await Sinco.goTo("https://drash.land") // as usual

• Added firefox support
• Removed waitForAnchorChange method

[ebebbington]

so im debating removing the waitForAnchorChange.. for context, the method looks like:

public async waitForAnchorChange(): Promise<void> {
    const notificationPromise = this
      .notification_resolvables["Page.navigatedWithinDocument"] = deferred();
    await notificationPromise;
    delete this.notification_resolvables["Page.navigatedWithinDocument"];
  }

It's not really a 'sought after method'
and it's used like:

await Sinco.type(..., "new val") // on chromestatus.com, theres an input field that changes the uri
await Sinco.waitForAnchorChange() // essentially waits until url is https://chromestatus.com/features#new%20val

But if i go to chromestatus.com, and change the value of the input field in the console manually, the uri doesn't change, but the chrome client does pick up an event for this in the tests

Alongside this, if i do the same with a firefox client, the client doesn't pick up any event for this

Is there a need for this method?