Use new GitHub templates. Add funding link (#8845)

.github/FUNDING.yml

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+custom: https://supporters.eff.org/donate/support-work-on-certbot

.github/issue_template.md

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+If you're having trouble using Certbot and aren't sure you've found a bug or
+request for a new feature, please first try asking for help at
+https://community.letsencrypt.org/. There is a much larger community there of
+people familiar with the project who will be able to more quickly answer your
+questions.
+
+## My operating system is (include version):
+
+
+## I installed Certbot with (snap, OS package manager, pip, certbot-auto, etc):
+
+
+## I ran this command and it produced this output:
+
+
+## Certbot's behavior differed from what I expected because:
+
+
+## Here is a Certbot log showing the issue (if available):
+###### Logs are stored in `/var/log/letsencrypt` by default. Feel free to redact domains, e-mail and IP addresses as you see fit.
+
+## Here is the relevant nginx server block or Apache virtualhost for the domain I am configuring:

.github/pull_request_template.md

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+## Pull Request Checklist
+
+- [ ] If the change being made is to a [distributed component](https://certbot.eff.org/docs/contributing.html#code-components-and-layout), edit the `master` section of `certbot/CHANGELOG.md` to include a description of the change being made.
+- [ ] Add or update any documentation as needed to support the changes in this PR.
+- [ ] Include your name in `AUTHORS.md` if you like.