fix(Xero): Fix showing Toggl Button in Xero

[EternallLight]

🌟 What does this PR do?

Fixes the broken selectors for Xero, so that Toggl Button appears in place.

🐛 Recommendations for testing

1. Sign in to Xero (we have test credentials)
2. Make sure the Toggl Button is visible:

📝 Links to relevant issues or information

#1910

[tiberiusuciu]

I kind of already asked for this on the question I asked on your other PR
But for Xero instead 😄

[tiberiusuciu]

Got the credentials 🙌

I was able to login, but I can't get past the screen that forces me to setup a multi-factor authentication.

II don't think I should be the one doing this 😅 Did you manage to get past it? Or did you create one temporarily and then disabled it?

[EternallLight]

It didn't ask me to. It might have became suspicious of why two people from different part of the globe logged in on the same day after weeks of no activity :)

[EternallLight]

@tiberiusuciu I have double-checked the fix – it wasn't there due to host selector changes and now it is. Looking 👌 as you can see from the screenshot.

[tiberiusuciu]

I was able to log in with Xero, it seems like this branch does not show the Toggl button on the header:

Is it supposed to only be visible on specific pages? 🤔

[EternallLight]

@tiberiusuciu it is supposed to be visible where the header is. I've recorded a short demo video: https://cln.sh/SHqBXr

[EternallLight]

Rebased and removed double-declarations from origins.js

[tiberiusuciu]

I think we made this repo private, but I can't seem to find the instruction on how to set up the extension locally to test it out. Could anyone refer me to this documentation? 👀

[EternallLight]

@tiberiusuciu

I've brought this up in Slack, but here's how I've been able to run it:

1. Clone git@github.com:toggl/track-extension-core.git and git@github.com:toggl/toggl-button.git side by side.
2. Do yarn install in the former.
3. Go to the toggl-button directory and do yarn link
4. Go to the toggl-extension-core directory and do yarn link "@toggl/track-extension"
5. Edit the resolve section of webpack.config.js to be the following:

  resolve: {
    extensions: ['.tsx', '.ts', '.js', '.jsx'],
    alias: {
      'webextension-polyfill': path.resolve(__dirname, 'node_modules/webextension-polyfill')
    }
  },

Not sure why, but it doesn't want to include webextension-polyfill from toggl-button/src/content without pointing directly to its location.
6. Run yarn start and enjoy the extension testing as before. When you change files to toggl-button, webpack rebuilds happen automagically.

[tiberiusuciu]

With the new repos on my machine and with the proper configuration, I was able to see the Toggl button visible on Xero.

It's working now! Let's just address the merge-conflict and this PR is good to go!