Fixes <https://bugs.gnu.org/36885>.
Reported by <lukasbf@tutanota.com>.
* gnu/installer/newt/page.scm (edit-file): New procedure.
(run-file-textbox-page): Add #:edit-button? and #:editor-locale
parameters. Remove 'file-text' and add 'edit-button', and add it
to the horizontal stacked grid when EXIT-BUTTON? is true. Wrap
body in 'loop'. Handle case where ARGUMENT is EDIT-BUTTON by calling
'loop'.
* gnu/installer/newt/final.scm (run-config-display-page): Add #:locale
parameter. Pass #:edit-button? and #:editor-locale to
'run-file-textbox-page'.
(run-final-page): Pass LOCALE to 'run-config-display-page'.