pw_ide: Enable cmake.format.allowOptionalArgumentIndentation

Keeps indenting style consistent for cmake files with current.

Test: `pw ide sync` adds entry. Format Document with entry properly
indents lines in CMakeLists.txt.

Change-Id: Icd9c99cc1bc9b4966516eb298d74fbd20580cd50
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/203638
Reviewed-by: Chad Norvell <chadnorvell@google.com>
Commit-Queue: David Rees <drees@google.com>
diff --git a/pw_ide/py/pw_ide/vscode.py b/pw_ide/py/pw_ide/vscode.py
index 86d89ce..7414ef5 100644
--- a/pw_ide/py/pw_ide/vscode.py
+++ b/pw_ide/py/pw_ide/vscode.py
@@ -110,6 +110,7 @@
 # alternative of instantiating with a list of tuples.
 _DEFAULT_SETTINGS: EditorSettingsDict = OrderedDict(
     {
+        "cmake.format.allowOptionalArgumentIndentation": True,
         "editor.detectIndentation": False,
         "editor.rulers": [80],
         "editor.tabSize": 2,