Dark mode support in welcome and 50x error pages. Prodded by Duncan Lock.

diff --git a/docs/html/50x.html b/docs/html/50x.html
index 7dd7c90..a57c2f9 100644
--- a/docs/html/50x.html
+++ b/docs/html/50x.html

@@ -3,6 +3,7 @@
 <head>
 <title>Error</title>
 <style>
+html { color-scheme: light dark; }
 body { width: 35em; margin: 0 auto;
 font-family: Tahoma, Verdana, Arial, sans-serif; }
 </style>

diff --git a/docs/html/index.html b/docs/html/index.html
index 09638f7..e8f5622 100644
--- a/docs/html/index.html
+++ b/docs/html/index.html

@@ -3,6 +3,7 @@
 <head>
 <title>Welcome to nginx!</title>
 <style>
+html { color-scheme: light dark; }
 body { width: 35em; margin: 0 auto;
 font-family: Tahoma, Verdana, Arial, sans-serif; }
 </style>