Ignore Backstitch files (new name for Godot Patchwork) (#2106)

As well as updating these lines for the rename, this also un-ignores the
launcher itself. Upstream, I proposed ignoring these in the template
<inkandswitch/backstitch-launcher#6> along with
some other files, but the rules to ignore the launcher were declined:

> For this PR, I'm keeping the launcher/updater checked into git -- I
> imagine most users would actually want the scripts checked in for easy
> dev work (otherwise everyone would have to come download the
> launcher!)

Resolves #2105

Author: wjt

.gitignore

@@ -31,12 +31,10 @@ __MACOSX
 # LibreOffice lock files, created while editing credits CSV files
 .~lock.*#
 
-# Godot Patchwork addon, bundled editor build, launcher, updater, and
-# config/state files
-.patchwork
-.patchwork_version
-/addons/patchwork/
+# Godot Backstitch addon, bundled editor build, and config/state files, from
+# https://github.com/inkandswitch/backstitch-launcher/blob/main/.gitignore.template
+/addons/backstitch/
 /godot_editor/
-launch-patchwork.exe
-patchwork.cfg
-update-patchwork.exe
+.backstitch_version
+/.backstitch/
+backstitch.cfg