add: download & about pages ; cover.css transfer to static & add icon.ico & website version complete

static/css/cover.css

@@ -0,0 +1,59 @@
+body {
+    box-shadow: inset 0 0 5rem rgba(0, 0, 0, .5);
+}
+
+.bd-placeholder-img {
+    font-size: 1.125rem;
+    text-anchor: middle;
+    -webkit-user-select: none;
+    -moz-user-select: none;
+    user-select: none;
+}
+
+@media (min-width: 768px) {
+    .bd-placeholder-img-lg {
+        font-size: 3.5rem;
+    }
+}
+
+.btn-secondary,
+.btn-secondary:hover,
+.btn-secondary:focus {
+    color: #333;
+    text-shadow: none;
+}
+
+.bg-image {
+    background-color: #89b3e7;
+}
+
+.cover-container {
+    max-width: 42em;
+}
+
+.nav-masthead .nav-link {
+    padding: .25rem 0;
+    font-weight: 700;
+    color: rgba(255, 255, 255, .5);
+    background-color: transparent;
+    border-bottom: .25rem solid transparent;
+}
+
+.nav-masthead .nav-link:hover,
+.nav-masthead .nav-link:focus {
+    border-bottom-color: rgba(255, 255, 255, .25);
+}
+
+.nav-masthead .nav-link + .nav-link {
+    margin-left: 1rem;
+}
+
+.nav-masthead .active {
+    color: #fff;
+    border-bottom-color: #fff;
+}
+
+.offcanvas, .modal-backdrop {
+    /* --bs-offcanvas-zindex: 1; */
+    --bs-backdrop-zindex: 1;
+}