docs: update download page to v5.5.15

Bump displayed English version and GitHub release URLs from v5.5.10 to v5.5.15
for both self-installing and stand-alone downloads.

Co-authored-by: GitHub Copilot <noreply@github.com>

Author: j4y

download.html

@@ -27,13 +27,13 @@ <h3>Install via package managers</h3>
 
 <ul id="download">
 
-    <li class="colorcop"><h3>English v5.5.10</h3>
+    <li class="colorcop"><h3>English v5.5.15</h3>
         <ul>
             <li class="dtype"><h4>self-installing</h4>
                 <ul>
                     <li class="typval">
                         <a class="lnk" title="download color cop"
-                           href="https://github.com/ColorCop/ColorCop/releases/download/v5.5.10/colorcop-setup.exe">
+                           href="https://github.com/ColorCop/ColorCop/releases/download/v5.5.15/colorcop-setup.exe">
                            colorcop-setup.exe
                         </a>
                     </li>
@@ -44,13 +44,13 @@ <h3>Install via package managers</h3>
         </ul>
 
     </li>
-    <li class="colorcop"><h3>English v5.5.10</h3>
+    <li class="colorcop"><h3>English v5.5.15</h3>
         <ul>
             <li class="dtype"><h4>stand-alone</h4>
                 <ul>
                     <li class="typval">
                         <a class="lnk" title="download color cop"
-                           href="https://github.com/ColorCop/ColorCop/releases/download/v5.5.10/colorcop.zip">
+                           href="https://github.com/ColorCop/ColorCop/releases/download/v5.5.15/colorcop.zip">
                            colorcop.zip
                         </a>
                     </li>