Notification list enhancements, fix striped tables on dark theme (#24639)

- Make code block rendering via backticks work
- Remove link color unless hovered
- Remove table stripes and fix stripes rendering on dark theme for other
tables
- Introduce new `button-link` class discussed previously for buttons
that look and act like links and apply it to the two right-side buttons
- Reduce box padding by 8px on each side
- Fix "Mark all read" button margin-right
- brighten `--color-markup-code-block` on arc-green

### Before
<img width="1216" alt="Screenshot 2023-05-10 at 20 00 30"
src="https://github.com/go-gitea/gitea/assets/115237/66da9ec2-dd09-4ef0-8f1d-1822a18b6b43">
<img width="1211" alt="Screenshot 2023-05-10 at 20 00 48"
src="https://github.com/go-gitea/gitea/assets/115237/f48e30a2-9a00-4723-93aa-79b97ca0ba0c">

### After
<img width="1222" alt="Screenshot 2023-05-10 at 20 09 59"
src="https://github.com/go-gitea/gitea/assets/115237/c956e0d0-b3d9-42a4-a3ed-f0431c22bf3f">
<img width="1218" alt="Screenshot 2023-05-10 at 20 05 34"
src="https://github.com/go-gitea/gitea/assets/115237/f72c1628-3961-4c28-9263-07cdf7531316">

web_src/css/base.css

@@ -1148,6 +1148,12 @@ a.ui.card:hover {
   border-top-color: var(--color-secondary-alpha-50);
 }
 
+.ui.striped.table > tr:nth-child(2n),
+.ui.striped.table > tbody > tr:nth-child(2n),
+.ui.basic.striped.table > tbody > tr:nth-child(2n) {
+  background: var(--color-light);
+}
+
 .ui.ui.ui.ui.table tr.active,
 .ui.ui.table td.active {
   color: var(--color-text);
@@ -2232,6 +2238,16 @@ a.ui.active.label:hover {
   border-left: none;
 }
 
+.ui.button.button-link {
+  background: transparent;
+  border: none;
+  color: inherit;
+}
+
+.ui.button.button-link:hover {
+  color: var(--color-primary);
+}
+
 .two-toggle-buttons .button:not(.active):first-of-type {
   border-right: none;
 }

web_src/css/helpers.css

@@ -163,6 +163,14 @@ Gitea's private styles use `g-` prefix.
 .gt-my-4 { margin-top: 1rem !important; margin-bottom: 1rem !important; }
 .gt-my-5 { margin-top: 2rem !important; margin-bottom: 2rem !important; }
 
+.gt-m-auto  { margin: auto !important; }
+.gt-mx-auto { margin-left: auto !important; margin-right: auto !important; }
+.gt-my-auto { margin-top: auto !important; margin-bottom: auto !important; }
+.gt-mt-auto { margin-top: auto !important; }
+.gt-mr-auto { margin-right: auto !important; }
+.gt-mb-auto { margin-bottom: auto !important; }
+.gt-ml-auto { margin-left: auto !important; }
+
 .gt-p-0 { padding: 0 !important; }
 .gt-p-1 { padding: .125rem !important; }
 .gt-p-2 { padding: .25rem !important; }

web_src/css/themes/theme-arc-green.css

@@ -151,7 +151,7 @@
   --color-menu: #2e323e;
   --color-card: #2e323e;
   --color-markup-table-row: #ffffff06;
-  --color-markup-code-block: #ffffff0d;
+  --color-markup-code-block: #ffffff16;
   --color-button: #353846;
   --color-code-bg: #2a2e3a;
   --color-code-sidebar-bg: #2e323e;