feat(config): preserve doc-style comments by default

Strip pass was eating JSDoc/Javadoc blocks. Add default preserve
patterns for /** blocks, /*! banners, /// and //! line docs.
Opt out by overriding preserve in .shush.toml.

internal/processor/testdata/multiline/doc_js.js

@@ -0,0 +1,16 @@
+/**
+ * Adds two numbers.
+ * @param {number} a
+ * @param {number} b
+ * @returns {number}
+ */
+function add(a, b) {
+  /*
+   * plain block comment
+   */
+  return a + b; // plain line comment
+}
+
+/*! license banner */
+/** single-line doc */
+function noop() {}

internal/processor/testdata/multiline/doc_js.js.golden

@@ -0,0 +1,13 @@
+/**
+ * Adds two numbers.
+ * @param {number} a
+ * @param {number} b
+ * @returns {number}
+ */
+function add(a, b) {
+  return a + b;
+}
+
+/*! license banner */
+/** single-line doc */
+function noop() {}

internal/processor/testdata/multiline/doc_rs.rs

@@ -0,0 +1,9 @@
+//! Crate-level docs.
+
+/// Adds two numbers.
+/// Returns the sum.
+pub fn add(a: i32, b: i32) -> i32 {
+    // plain line comment
+    /* plain block comment */
+    a + b
+}

internal/processor/testdata/multiline/doc_rs.rs.golden

@@ -0,0 +1,7 @@
+//! Crate-level docs.
+
+/// Adds two numbers.
+/// Returns the sum.
+pub fn add(a: i32, b: i32) -> i32 {
+    a + b
+}