Install custom LSS script to /usr/local/share/fish on make install

Decided to move doc_src/fish.lss to share/lynx.lss, which just makes
more sense all around. Accordingly, now using {$__fish_datadir} instead
of {$__fish_help_dir} in help.fish.

Makefile now installs the custom lss on make install

(cherry picked from commit 338311af1e)

Makefile.in

@@ -714,6 +714,8 @@ install-force: all install-translations install-doc | show-datadir show-sysconfd
 		$(INSTALL) -m 644 $$i $(DESTDIR)$(mandir)/man1/; \
 		true; \
 	done;
+	@echo "Installing miscellaneous helper resources";
+	$v $(INSTALL) -m 644 share/lynx.lss $(DESTDIR)$(datadir)/fish/
 .PHONY: install-force
 
 #

share/functions/help.fish

@@ -152,7 +152,7 @@ function help --description 'Show help for the fish shell'
         # by using a custom style sheet. See https://github.com/fish-shell/fish-shell/issues/4170
         set -l local_file 0
         if eval $fish_browser --version 2>/dev/null | string match -qr Lynx
-            set fish_browser $fish_browser -lss={$__fish_help_dir}/fish.lss
+            set fish_browser $fish_browser -lss={$__fish_datadir}/lynx.lss
         end
         eval $fish_browser $page_url
     end