[base64-dark theme] Change active line color to distinguish it from selection

theme/base16-dark.css

@@ -32,5 +32,5 @@
 .cm-s-base16-dark span.cm-link {color: #aa759f;}
 .cm-s-base16-dark span.cm-error {background: #ac4142; color: #b0b0b0;}
 
-.cm-s-base16-dark .CodeMirror-activeline-background {background: #2F2F2F !important;}
+.cm-s-base16-dark .CodeMirror-activeline-background {background: #202020 !important;}
 .cm-s-base16-dark .CodeMirror-matchingbracket { text-decoration: underline; color: white !important;}