add spacing between sign in button's icon and text (#33609)

This pull request edits the head_navbar template and adds spacing
between the icon and the text inside the sign in button of the navbar
(button which displays at the top right of Gitea's pages when the user
is not signed in).

It bugged me that there was no spacing between the button's contents so
I test ran this change quickly on my server and thought it looked a lot
better, so decided to make this pull request. Up to you to decide if you
agree that it looks better :)

templates/base/head_navbar.tmpl

@@ -175,11 +175,13 @@
 		{{else}}
 			{{if .ShowRegistrationButton}}
 				<a class="item{{if .PageIsSignUp}} active{{end}}" href="{{AppSubUrl}}/user/sign_up">
-					{{svg "octicon-person"}} {{ctx.Locale.Tr "register"}}
+					{{svg "octicon-person"}}
+					<span class="tw-ml-1">{{ctx.Locale.Tr "register"}}</span>
 				</a>
 			{{end}}
 			<a class="item{{if .PageIsSignIn}} active{{end}}" rel="nofollow" href="{{AppSubUrl}}/user/login{{if not .PageIsSignIn}}?redirect_to={{.CurrentURL}}{{end}}">
-				{{svg "octicon-sign-in"}} {{ctx.Locale.Tr "sign_in"}}
+				{{svg "octicon-sign-in"}}
+				<span class="tw-ml-1">{{ctx.Locale.Tr "sign_in"}}</span>
 			</a>
 		{{end}}
 	</div><!-- end full right menu -->