Add spinner to py-editor run buttons (#2078)

* Add spinner to disabled py-editor run buttons

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* css nit suggested by WebReflection

---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

CHANGELOG.md

@@ -1,5 +1,15 @@
 # Release Notes
 
+## 2024.05.21
+
+### Features
+
+### Bug fixes
+
+### Enhancements
+
+-   `py-editor` run buttons now display a spinner when disabled, which occurs when the editor is running code.
+
 ## 2023.05.01
 
 ### Features

pyscript.core/src/core.css

@@ -42,3 +42,34 @@ mpy-config {
 .mpy-editor-run-button:disabled {
     opacity: 1;
 }
+
+@keyframes spinner {
+    to {
+        transform: rotate(360deg);
+    }
+}
+.py-editor-run-button:disabled > *,
+.mpy-editor-run-button:disabled > * {
+    display: none; /* hide all the child elements of the run button when it is disabled */
+}
+.py-editor-run-button:disabled,
+.mpy-editor-run-button:disabled {
+    border-width: 0;
+}
+.py-editor-run-button:disabled::before,
+.mpy-editor-run-button:disabled::before {
+    content: "";
+    box-sizing: border-box;
+    position: absolute;
+    top: 100%;
+    left: 100%;
+    width: 20px;
+    height: 20px;
+    margin-top: -23px; /* hardcoded value to center the spinner on the run button */
+    margin-left: -26px; /* hardcoded value to center the spinner on the run button */
+    border-radius: 50%;
+    border: 2px solid #aaa;
+    border-top-color: #000;
+    background-color: #fff;
+    animation: spinner 0.6s linear infinite;
+}