Fix: Theme milestone progress bar statuses not rendered correctly

Fixes Milestones progress bar statuses not rendered correctly after Gitea
1.23.x update. Adds explicit styling for progress bars, using theme colours.
Fixes #133

public/assets/css/theme-bthree-dark.css

@@ -517,3 +517,21 @@ a.ui.primary.label:hover,
  .CodeMirror.cm-s-default .cm-error, .CodeMirror.cm-s-paper .cm-error {
 	 color: #dbdbeb;
 }
+
+/* Progress bar. */
+progress {
+  appearance: none; /* Remove default styling */
+  background-color: var(--color-secondary); /* Fallback colour bg (unfilled portion) */
+  border: none; /* remove default border */
+
+  -moz-appearance: none;
+  -webkit-appearance: none;
+}
+
+progress::-webkit-progress-value {
+  background-color: var(--color-primary); /* Color of the filled portion */
+}
+
+progress::-moz-progress-bar {
+  background-color: var(--color-primary); /* Color of the filled portion */
+}