[docs] Add some docs for `flake8-simplify` (#3027)

crates/ruff/src/rules/flake8_simplify/rules/ast_bool_op.rs

@@ -13,6 +13,32 @@ use crate::registry::Diagnostic;
 use crate::violation::AlwaysAutofixableViolation;
 
 define_violation!(
+    /// ## What it does
+    /// Checks for multiple `isinstance` calls on the same target.
+    ///
+    /// ## Why is this bad?
+    /// To check if an object is an instance of any one of multiple types
+    /// or classes, it is unnecessary to use multiple `isinstance` calls, as
+    /// the second argument of the `isinstance` built-in function accepts a
+    /// tuple of types and classes.
+    ///
+    /// Using a single `isinstance` call implements the same behavior with more
+    /// concise code and clearer intent.
+    ///
+    /// ## Example
+    /// ```python
+    /// if isinstance(obj, int) or isinstance(obj, float):
+    ///     pass
+    /// ```
+    ///
+    /// Use instead:
+    /// ```python
+    /// if isinstance(obj, (int, float)):
+    ///     pass
+    ///
+    /// ## References
+    /// * [Python: "isinstance"](https://docs.python.org/3/library/functions.html#isinstance)
+    /// ```
     pub struct DuplicateIsinstanceCall {
         pub name: String,
     }

crates/ruff/src/rules/flake8_simplify/rules/ast_with.rs

@@ -12,6 +12,33 @@ use crate::violation::{AutofixKind, Availability, Violation};
 use super::fix_with;
 
 define_violation!(
+    /// ## What it does
+    /// Checks for the unnecessary nesting of multiple consecutive context
+    /// managers.
+    ///
+    /// ## Why is this bad?
+    /// In Python 3, a single `with` block can include multiple context
+    /// managers.
+    ///
+    /// Combining multiple context managers into a single `with` statement
+    /// will minimize the indentation depth of the code, making it more
+    /// readable.
+    ///
+    /// ## Example
+    /// ```python
+    /// with A() as a:
+    ///     with B() as b:
+    ///         pass
+    /// ```
+    ///
+    /// Use instead:
+    /// ```python
+    /// with A() as a, B() as b:
+    ///     pass
+    /// ```
+    ///
+    /// ## References
+    /// * [Python: "The with statement"](https://docs.python.org/3/reference/compound_stmts.html#the-with-statement)
     pub struct MultipleWithStatements {
         pub fixable: bool,
     }