Dark stylesheet improvement

- Replace css filter with a border
- Replacae "background" with "background-color" since "background" does
  a bunch of other things too.

assets/css/dark.css

@@ -1,15 +1,13 @@
 @media (prefers-color-scheme: dark) {
 	html {
-		background: #000;
-		color: #fff;
+		/*"background" is short for a bunch of unnecessary CSS rules; background-color is all I need*/
+		background-color: #000;
+		color: #eee; /*I've been told that pure white on black is a bit harsh*/
 	}
 
 	/* IndieWeb u-photo shouldn't look like floating punctuation marks */
 	.u-photo {
-		/* Versions of Samsung Internet released recently as 2017 need this
-		 * prefix, along with Qt4-based QtWebkit used in e.g. rekonq */
-		-webkit-filter: invert(1);
-		filter: invert(1);
+		border: 1px solid #ddc;	
 	}
 
 	a {

assets/css/main.css

@@ -57,6 +57,7 @@ nav li {
 	}
 }
 
+/* center images that aren't my indieweb icon */
 img:not(.u-photo) {
 	display: block;
 	height: auto;