Add rofi config; use rofi as app launcher in i3 on roxy

.config/rofi/config.rasi

@@ -0,0 +1,19 @@
+configuration {
+    // Set default modi
+    modi: "window,run,drun";
+
+    // Autodetect DPI
+    dpi: 0;
+
+    // Continuous scrolling (line-by-line instead of page-wise)
+    scroll-method: 1;
+
+    // When running shell commands in a terminal, pause before exiting
+    run-shell-command: "{terminal} -e 'bash -ic \"{cmd} && read\"'";
+
+    // Keybindings: Autocomplete with Tab
+    kb-row-select: "Control+space,Tab";
+    kb-row-tab: "";
+}
+
+@theme "/usr/share/rofi/themes/Monokai.rasi"