Improve CSS for equation numbers.

Ref: readthedocs/sphinx_rtd_theme#383 (comment)

Author: rdzman

css/matpower.css

@@ -1,75 +1,36 @@
 /* matpower.css */
-/* 
-MathJax {
-    vertical-align: middle;
-}
-div.math {
-    vertical-align: middle;
-}
-.eqno {
-    float: right;
-}
- */
-
-/* From https://github.com/readthedocs/sphinx_rtd_theme/pull/383#issuecomment-348803509 */
+/* Based on ...
+   https://github.com/readthedocs/sphinx_rtd_theme/pull/383#issuecomment-348803509
+   https://github.com/readthedocs/sphinx_rtd_theme/pull/383#issuecomment-1894862745
+*/
 div.math {
     position: relative;
     padding-right: 2.5em;
 }
-.eqno {
+span.eqno {
     height: 100%;
     position: absolute;
     right: 0;
     padding-left: 5px;
     padding-bottom: 5px;
     padding-right: 1px;
 }
-.eqno:before {
+span.eqno:before {
     display: inline-block;
     height: 100%;
     vertical-align: middle;
     content: "";
 }
-.eqno .headerlink {
-    display: none;
-    visibility: hidden;
-    font-size: 14px;
-    padding-left: .3em;
-}
-.eqno:hover .headerlink {
-    display: inline-block;
-    visibility: hidden;
-    margin-right: -1.05em;
-}
-.eqno .headerlink:after {
-    visibility: visible;
-    content: "\f0c1";
-    font-family: FontAwesome;
-    display: inline-block;
-    margin-left: -.9em;
+span.eqno a.headerlink {
+    position: relative;
+    z-index: 1;
 }
 .MathJax_Display {
     max-width: 100%;
     overflow-x: auto;
     overflow-y: hidden;
 }
 
-/*
-..eqno {
-    margin-left: 5px;
-    float: right;
-}
-.math .headerlink {
-    display: none;
-    visibility: hidden;
-}
-.math:hover .headerlink {
-    display: inline-block;
-    visibility: visible;
-    margin-right: -0.7em;
-}
-*/
-
 /* admonition title */
 .rst-content .admonition .admonition-title, .rst-content .note .admonition-title, .rst-content .note .wy-alert-title, .rst-content .seealso .admonition-title, .rst-content .seealso .wy-alert-title, .rst-content .wy-alert-info.admonition-todo .admonition-title, .rst-content .wy-alert-info.admonition-todo .wy-alert-title, .rst-content .wy-alert-info.admonition .admonition-title, .rst-content .wy-alert-info.admonition .wy-alert-title, .rst-content .wy-alert-info.attention .admonition-title, .rst-content .wy-alert-info.attention .wy-alert-title, .rst-content .wy-alert-info.caution .admonition-title, .rst-content .wy-alert-info.caution .wy-alert-title, .rst-content .wy-alert-info.danger .admonition-title, .rst-content .wy-alert-info.danger .wy-alert-title, .rst-content .wy-alert-info.error .admonition-title, .rst-content .wy-alert-info.error .wy-alert-title, .rst-content .wy-alert-info.hint .admonition-title, .rst-content .wy-alert-info.hint .wy-alert-title, .rst-content .wy-alert-info.important .admonition-title, .rst-content .wy-alert-info.important .wy-alert-title, .rst-content .wy-alert-info.tip .admonition-title, .rst-content .wy-alert-info.tip .wy-alert-title, .rst-content .wy-alert-info.warning .admonition-title, .rst-content .wy-alert-info.warning .wy-alert-title, .rst-content .wy-alert.wy-alert-info .admonition-title, .wy-alert.wy-alert-info .rst-content .admonition-title, .wy-alert.wy-alert-info .wy-alert-title {
     background: #568085;