Fix documentation and coding style in recent xwidget commits

Fix documentation and coding style in recent xwidget commits

* src/xwidget.c (Fmake_xwidget, find_widget)
(xwidget_motion_or_crossing, xwidget_button_1, xwidget_button):
Fix style in comments.
(Fxwidget_perform_lispy_event): Doc fix.
* src/xwidget.c (set_widget_if_text_view, kill_frame_xwidget_views):
* src/keyboard.c (make_lispy_event): Fix style of braces.

* lisp/xwidget.el (xwidget-webkit-isearch-mode): Fix keys in doc
string.

* doc/lispref/commands.texi (Xwidget Events): Fix markup and
wording.
* doc/lispref/display.texi (Xwidgets): Fix wording and markup.
* doc/emacs/misc.texi (Embedded WebKit Widgets): Fix wording.

* etc/NEWS: Fix wording and punctuation.