Added a theme class that loads the theme from config

nw/themes/default/styles.css

@@ -0,0 +1,18 @@
+* {
+    background-color: #999999;
+}
+
+QTextEdit {
+    background-color: #141414;
+    color: #c7cfd0;
+}
+
+QTextBrowser {
+    background-color: #141414;
+    color: #c7cfd0;
+    /* padding: 40px; */
+}
+
+QTreeView, QHeaderView {
+    font-size: 13px;
+}

nw/themes/default/theme.conf

@@ -0,0 +1,11 @@
+[Syntax]
+headertext     =   0, 155, 200
+headertag      =   0, 105, 135
+emphasis       = 200, 120,   0
+straightquotes = 200,  46,   0
+doublequotes   = 184, 200,   0
+singlequotes   = 136, 200,   0
+hidden         = 150, 150, 150
+keyword        = 200,  46,   0
+value          = 184, 200,   0
+spellcheckline = 200,  46,   0