feat: new backend issue template (#8449)

## Description of changes

the feature template has more than needed to request a new backend; this
will also auto-label w/ "new backend"

also some light editing of the other templates for consistency

## Issues closed

.github/ISSUE_TEMPLATE/bug-report.yml

@@ -1,5 +1,5 @@
-name: Bug Report
-description: File a bug report
+name: Bug report
+description: File a bug report for Ibis
 title: "bug: "
 labels: ["bug"]
 body:

.github/ISSUE_TEMPLATE/docs-issue.yml

@@ -1,4 +1,4 @@
-name: Documentation Issue
+name: Documentation issue
 description: Open an issue about the Ibis documentation
 title: "docs: "
 labels: ["docs"]

.github/ISSUE_TEMPLATE/feature-request.yml

@@ -1,5 +1,5 @@
-name: Feature Request
-description: Suggest an idea for ibis
+name: Feature request
+description: Suggest an idea for Ibis
 title: "feat: "
 labels: ["feature"]
 body:

.github/ISSUE_TEMPLATE/new-backend.yml

@@ -0,0 +1,24 @@
+name: New backend request
+description: Suggest a new backend for Ibis
+title: "feat: "
+labels: ["feature", "new backend"]
+body:
+  - type: markdown
+    attributes:
+      value: Thanks for taking the time to fill out a new backend request!
+  - type: textarea
+    id: backend
+    attributes:
+      label: Which new backend would you like to see in Ibis?
+      description: Please provide relevant links and disclose your affiliation with the backend.
+      placeholder: "I would like a new backend for ..."
+    validations:
+      required: true
+  - type: checkboxes
+    id: terms
+    attributes:
+      label: Code of Conduct
+      description: By submitting this issue, you agree to follow our [Code of Conduct](https://github.com/ibis-project/ibis/blob/main/CODE_OF_CONDUCT.md)
+      options:
+        - label: I agree to follow this project's Code of Conduct
+          required: true