feat(lint): add noSharedBranchCode (#12889)

Author: dyc3

.changeset/add-no-shared-branch-code-rule.md

@@ -0,0 +1,15 @@
+---
+"@biomejs/biome": patch
+---
+
+Added the nursery rule [`noSharedBranchCode`](https://biomejs.dev/linter/rules/no-shared-branch-code/), which reports code that is repeated at the start or end of every branch of an `if` statement. That code runs no matter which branch is taken, so it can be moved before or after the `if` statement.
+
+```js
+if (condition) {
+  doSomething();
+  cleanup();
+} else {
+  doSomethingElse();
+  cleanup();
+}
+```