Added escape sequence "\a" (audible bell, 0x07) to Utils.parseEscapedChars().

The sequece is part of C and C++ standard, as well as protocol buffer encoding.

- https://en.wikipedia.org/wiki/Escape_sequences_in_C
- https://en.cppreference.com/w/cpp/language/escape
- https://developers.google.com/protocol-buffers/docs/text-format-spec#string

tests/operations/tests/UnescapeString.mjs

@@ -0,0 +1,55 @@
+/**
+ * UnescapeString tests.
+ *
+ * @copyright Crown Copyright 2022
+ * @license Apache-2.0
+ */
+import TestRegister from "../../lib/TestRegister.mjs";
+
+TestRegister.addTests([
+    {
+        name: "UnescapeString: escape sequences",
+        input: "\\a\\b\\f\\n\\r\\t\\v\\'\\\"",
+        expectedOutput: String.fromCharCode(0x07, 0x08, 0x0c, 0x0a, 0x0d, 0x09,
+            0x0b, 0x27, 0x22),
+        recipeConfig: [
+            {
+                op: "Unescape string",
+                args: [],
+            },
+        ],
+    },
+    {
+        name: "UnescapeString: octals",
+        input: "\\0\\01\\012\\1\\12",
+        expectedOutput: String.fromCharCode(0, 1, 10, 1, 10),
+        recipeConfig: [
+            {
+                op: "Unescape string",
+                args: [],
+            },
+        ],
+    },
+    {
+        name: "UnescapeString: hexadecimals",
+        input: "\\x00\\xAA\\xaa",
+        expectedOutput: String.fromCharCode(0, 170, 170),
+        recipeConfig: [
+            {
+                op: "Unescape string",
+                args: [],
+            },
+        ],
+    },
+    {
+        name: "UnescapeString: unicode",
+        input: "\\u0061\\u{0062}",
+        expectedOutput: "ab",
+        recipeConfig: [
+            {
+                op: "Unescape string",
+                args: [],
+            },
+        ],
+    },
+]);