doc(Home): update link address (#6520)

* doc: 调整 Home 页面 Header 间隙

* doc: 更新加入我们地址链接

* doc: 更新贡献指南链接

Author: ArgoZhang

src/BootstrapBlazor.Server/Components/Layout/HomeLayout.razor

@@ -47,13 +47,13 @@
             <h4>@Localizer["Community"]</h4>
             <ul>
                 <li>
-                    <div class="footer-link">@Localizer["CommunityLi2"]</div>
+                    <div class="footer-link"><a href="https://github.com/BootstrapBlazor/membership/issues" target="_blank">@Localizer["CommunityLi2"]</a></div>
                 </li>
                 <li>
-                    <div class="footer-link">@Localizer["CommunityLi1"]</div>
+                    <div class="footer-link"><a href="https://github.com/dotnetcore/BootstrapBlazor?tab=coc-ov-file#readme" target="_blank">@Localizer["CommunityLi1"]</a></div>
                 </li>
                 <li>
-                    <div class="footer-link">@Localizer["CommunityLi3"]</div>
+                    <div class="footer-link"><a href="https://github.com/dotnetcore/BootstrapBlazor/issues" target="_blank">@Localizer["CommunityLi3"]</a></div>
                 </li>
             </ul>
         </div>

src/BootstrapBlazor.Server/Components/Pages/Index.razor.css

@@ -4,8 +4,9 @@
     --bd-pink-rgb: 214, 51, 132;
     --bd-violet-rgb: 112.520718, 44.062154, 249.437846;
     --bd-accent-rgb: 255, 228, 132;
-    padding-top: 3rem;
+    padding-top: calc(3rem + var(--bs-header-height));
     background-image: linear-gradient(180deg, rgba(var(--bs-body-bg-rgb), 0.01), rgba(var(--bs-body-bg-rgb), 1) 85%), radial-gradient(ellipse at top left, rgba(var(--bs-primary-rgb), 0.5), transparent 50%), radial-gradient(ellipse at top right, rgba(var(--bd-accent-rgb), 0.5), transparent 50%), radial-gradient(ellipse at center right, rgba(var(--bd-violet-rgb), 0.5), transparent 50%), radial-gradient(ellipse at center left, rgba(var(--bd-pink-rgb), 0.5), transparent 50%);
+    margin-top: calc(0px - var(--bs-header-height));
 }
 
     .bd-masthead h1 {