Add OpenCollective Contributors to README

[monkeywithacupcake]

Hi, I'm making updates for Open Collective. Either you or another core contributor signed this repository up for Open Collective. This pull request adds financial contributors from your Open Collective https://opencollective.com/jenssegers-blade ❤️

What it does:

• adds a badge to show the latest number of financial contributors
• adds a banner displaying contributors to the project on GitHub
• adds a banner displaying all individuals contributing financially on Open Collective
• adds a section displaying all organizations contributing financially on Open Collective, with their logo and a link to their website

P.S: As with any pull request, feel free to comment or suggest changes.

Thank you for your great contribution to the Open Source community. You are awesome! 🙌
And welcome to the Open Collective community! 😊

Come chat with us in the #opensource channel on https://slack.opencollective.com - great place to ask questions and share best practices with other Open Source sustainers!

[coveralls]

Coverage remained the same at 58.621% when pulling c9e3612 on monkeywithacupcake:patch-1 into 8dc7d31 on jenssegers:master.

[coveralls]

Coverage remained the same at 58.621% when pulling c9e3612 on monkeywithacupcake:patch-1 into 8dc7d31 on jenssegers:master.