Adds documentation for analyzers

docs/input/analyzer/rules/RULE_TEMPLATE.md

@@ -0,0 +1,38 @@
+---
+Title: SpectreXxxx
+Description: Rule title
+Category: Usage
+Severity: Hidden, Info, Warning, or Error
+Excluded: true
+---
+
+## Cause
+
+A concise-as-possible description of when this rule is violated. If there's a lot to explain, begin with "A violation of this rule occurs when..."
+
+## Reason for rule
+
+Explain why the user should care about the violation.
+
+## How to fix violations
+
+To fix a violation of this rule, [describe how to fix a violation].
+
+## Examples
+
+### Violates
+
+Example(s) of code that violates the rule.
+
+### Does not violate
+
+Example(s) of code that does not violate the rule.
+
+## How to suppress violations
+
+**If the severity of your analyzer isn't _Warning_, delete this section.**
+
+```csharp
+#pragma warning disable Spectre1000 // <Rule name>
+#pragma warning restore Spectre1000 // <Rule name>
+```