Wrap the setting of basic whitespace formatting options in a conditional
block, following the de facto standard.
Setting 'et', 'sts' and 'sw' can be disabled by setting
"gleam_recommended_style" to false.
Follow up to PR #17086.
closes: #17128
Signed-off-by: Doug Kearns <dougkearns@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>