Fixes the anchors for footnotes in markdown, resolves sighingnow#109

Signed-off-by: Tao He <sighingnow@gmail.com>

Author: sighingnow

_includes/body.html

@@ -38,3 +38,6 @@ <h1 id="{{ page.id }}">{{ site.title | escape }}</h1>
 {% if page.mermaid %}
     {% include mermaid.html %}
 {% endif %}
+
+<!-- introduce mathjax support -->
+{% include fixes-chrome-anchors.html %}

_includes/fixes-chrome-anchors.html

@@ -0,0 +1,20 @@
+<script>
+    function fixes_chrome_anchors() {
+        let chrome = /Chrome/.test(navigator.userAgent) && /Google Inc/.test(navigator.vendor);
+        if (window.location.hash && chrome) {
+            setTimeout(function () {
+                var hash = window.location.hash;
+                window.location.hash = "";
+                window.location.hash = hash;
+            }, 300);
+        }
+    }
+
+    if (document.readyState === "loading") {
+        // Loading hasn't finished yet
+        document.addEventListener("DOMContentLoaded", fixes_chrome_anchors);
+    } else {
+        // `DOMContentLoaded` has already fired
+        fixes_chrome_anchors();
+    }
+</script>

_posts/2023-12-12-footnotes.md

@@ -0,0 +1,125 @@
+---
+title: Using Footnotes
+author: Tao He
+date: 2023-12-12
+category: Jekyll
+layout: post
+mermaid: true
+---
+
+This jekyll-theme supports [MathJax](https://www.mathjax.org/) to render footnotes
+in markdown.
+
+e.g.,
+
+```markdown
+The well known Pythagorean theorem $x^2 + y^2 = z^2$ was
+proved to be invalid for other exponents[^1].
+Meaning the next equation has no integer solutions:
+
+$$ x^n + y^n = z^n $$
+```
+
+The well known Pythagorean theorem $x^2 + y^2 = z^2$ was
+proved to be invalid for other exponents[^1].
+Meaning the next equation has no integer solutions:
+
+$$ x^n + y^n = z^n $$
+
+Long contents
+-------------
+
+long contents .....
+
+1. a
+2. b
+3. c
+4. d
+
+### Sub title 1
+
+### Sub title 2
+
+### Sub title 3
+
+Long contents
+-------------
+
+long contents .....
+
+1. a
+2. b
+3. c
+4. d
+
+### Sub title 1
+
+### Sub title 2
+
+### Sub title 3
+
+Long contents
+-------------
+
+long contents .....
+
+1. a
+2. b
+3. c
+4. d
+
+### Sub title 1
+
+### Sub title 2
+
+### Sub title 3
+
+Long contents
+-------------
+
+long contents .....
+
+1. a
+2. b
+3. c
+4. d
+
+### Sub title 1
+
+### Sub title 2
+
+### Sub title 3
+
+Long contents
+-------------
+
+long contents .....
+
+1. a
+2. b
+3. c
+4. d
+
+### Sub title 1
+
+### Sub title 2
+
+### Sub title 3
+
+Long contents
+-------------
+
+long contents .....
+
+1. a
+2. b
+3. c
+4. d
+
+### Sub title 1
+
+### Sub title 2
+
+### Sub title 3
+
+[^1]: [https://en.wikipedia.org/wiki/Fermat%27s_Last_Theorem](https://en.wikipedia.org/wiki/Fermat%27s_Last_Theorem)