Better handling of escaped quotes in textual item (#1557)

Fixes #1551

## Checklist

- [x] I have added
[tests](https://www.cursorless.org/docs/contributing/test-case-recorder/)
- [ ] I have updated the
[docs](https://github.com/cursorless-dev/cursorless/tree/main/docs) and
[cheatsheet](https://github.com/cursorless-dev/cursorless/tree/main/cursorless-talon/src/cheatsheet)
- [ ] I have not broken the cheatsheet

Author: AndreasArvidsson

packages/cursorless-engine/src/processTargets/modifiers/ItemStage/tokenizeRange.ts

@@ -41,8 +41,8 @@ export function tokenizeRange(
   const lexemes = text
     // NB: Both the delimiters and the text between them are included because we
     // use a capture group in this split regex
-    .split(/([,(){}<>[\]"'`]|\\"|\\'|\\`)/g)
-    .filter((lexeme) => lexeme.length > 0);
+    .split(/([,(){}<>[\]"'`])|(?<!\\)(\\"|\\'|\\`)/g)
+    .filter((lexeme) => lexeme != null && lexeme.length > 0);
   const joinedLexemes = joinLexemesBySkippingMatchingPairs(lexemes);
   const tokens: Token[] = [];
   let offset = document.offsetAt(interior.start);

packages/cursorless-vscode-e2e/src/suite/fixtures/recorded/itemTextual/clearItem19.yml

@@ -0,0 +1,30 @@
+languageId: plaintext
+command:
+  version: 5
+  spokenForm: clear item
+  action: {name: clearAndSetSelection}
+  targets:
+    - type: primitive
+      modifiers:
+        - type: containingScope
+          scopeType: {type: collectionItem}
+  usePrePhraseSnapshot: true
+initialState:
+  documentContents: |-
+    values = {
+        "aaa": "\\",
+        "bbb": "ccc",
+    }
+  selections:
+    - anchor: {line: 1, character: 4}
+      active: {line: 1, character: 4}
+  marks: {}
+finalState:
+  documentContents: |-
+    values = {
+        ,
+        "bbb": "ccc",
+    }
+  selections:
+    - anchor: {line: 1, character: 4}
+      active: {line: 1, character: 4}