feat: display theme version in footer (#1611)

_includes/footer.html

@@ -34,7 +34,14 @@
     {%- endcapture -%}
 
     {%- capture _theme -%}
-      <a href="https://github.com/cotes2020/jekyll-theme-chirpy" target="_blank" rel="noopener">Chirpy</a>
+      <a
+        data-bs-toggle="tooltip"
+        data-bs-placement="top"
+        title="v{{ theme.version }}"
+        href="https://github.com/cotes2020/jekyll-theme-chirpy"
+        target="_blank"
+        rel="noopener"
+      >Chirpy</a>
     {%- endcapture -%}
 
     {{ site.data.locales[include.lang].meta | replace: ':PLATFORM', _platform | replace: ':THEME', _theme }}