chore(gh): Add new-lint issue template (rust-lang#15575)

### What does this PR try to resolve?

We aren't quite ready for writing lints (waiting on an annotate-snippets
release) but I wanted to start recording some lint ideas I had.

### How should we test and review this PR?

Based on clippy's which I assumed would be a good starting point. There
are more area we'll need to fill out during discussion, like the lint
name, what primary group the lint would be in, etc.

### Additional information

Author: weihanglo

.github/ISSUE_TEMPLATE/new_lint.yml

@@ -0,0 +1,48 @@
+name: New lint suggestion
+description: Suggest a new Cargo lint.
+labels: ["A-new-lint", "S-triage"]
+body:
+  - type: markdown
+    attributes:
+      value: Thank you for your lint idea!
+  - type: textarea
+    id: what
+    attributes:
+      label: What it does
+      description: What does this lint do?
+    validations:
+      required: true
+  - type: textarea
+    id: advantage
+    attributes:
+      label: Advantage
+      description: >
+        What is the advantage of the recommended code over the original code?
+      placeholder: |
+        - Remove bounds check inserted by ...
+        - Remove the need to duplicate/store ...
+        - Remove typo ...
+  - type: textarea
+    id: drawbacks
+    attributes:
+      label: Drawbacks
+      description: What might be possible drawbacks of such a lint?
+  - type: textarea
+    id: example
+    attributes:
+      label: Example
+      description: >
+        Include a short example showing when the lint should trigger together
+        with the improved code.
+      value: |
+        ```toml
+        <code>
+        ```
+
+        Could be written as:
+
+        ```toml
+        <code>
+        ```
+    validations:
+      required: true