Potential slack-libpurple doc update

Readme.md

To create the login token for the Slack plugin.

1. Login to Slack in Chrome
2. Open the developer tools (either press F12, or menu -> More Tools -> Developer Tools)
3. Enter into the console Object.values(JSON.parse(localStorage["localConfig_v2"]).teams).find(a => a.domain == 'myslackdomain').token replacing myslackdomain with the part of your Slack that's before the .slack.com website url eg, for https://example.slack.com you would use example This should start with "xoxc-..."
4. Switch to the 'Application' tab, then expand the 'Cookies' menu on the left and click on the first domain in the list
5. Look for a cookie with a name of 'd' which should have a value that starts with "xoxd-"
6. Open notepad and take the two values and separate them with a space. The value should look like this: xoxc-... xoxd-....
7. Use this value as the 'password' for the account in Pidgin/bitlbee/spectrum2

Looks good, but in step #3, add full stop (period) between '... use example', 'This should start with...'.