Create PR from when triggered by webhook

As CNCF adds new members to Salesforce, we want to be able to automatically create pull requests with the new member's info.

1. Create a GitHub Action that listens for a webhook from the Linux Foundation Salesforce.
2. Define an API of the possible keys to be added, changed, or removed.
3. When a webhook POST is received, CNCF-Bot should create a branch with the new or changed information and open a PR.
4. Demonstrate how you can use a set of `curl` commands to show that all the functionality is working.

The initial version should support creating, removing, or updating a member. Additionally, it should support adding a member to be a KCSP or KTP. If the SVG is included in the POST, that also needs to be written to `hosted_logos`, in addition to modifying `landscape.yml`.

Once things are working on this side, we'll have a Salesforce expert implement the triggers that call out to the webhook when CNCF members change:
https://salesforce.stackexchange.com/questions/64253/creation-of-a-public-api/64260#64260
https://salesforce.stackexchange.com/questions/93831/i-need-to-integrate-an-external-system-with-salesforce-using-webhooks/180199
https://moometric.com/integrations/sf/salesforce-visual-workflow-plugin-post-json-callout-external-webservice/
https://stackoverflow.com/questions/13121688/web-hook-in-salesforce