add footer

lib/html_body.typ

@@ -7,6 +7,8 @@
 #let html_body(
   /// The visible header of the page
   header: none,
+  /// The footer of the page
+  footer: none,
   /// Logo of the site
   logo: none,
   /// Navigation menu content, css style expect a list
@@ -15,7 +17,14 @@
 ) = {
   theme-colors-css
   ```raw-css
+
+  html, body {
+    height: 100%;
+    margin: 0;
+  }
+
   site-wrapper {
+    height: 100%;
     display: flex;
     flex-wrap: wrap;
     width: 100%;
@@ -33,6 +42,8 @@
     }
   
     site-container {
+      display: flex;
+      flex-direction: column;
       width: 1050px;
       padding: 0 20px;
   
@@ -45,6 +56,16 @@
         border-bottom: solid 1px var(--color-border);
         margin-top: 15px;
       }
+
+      main {
+        flex: 1;
+      }
+
+      footer {
+        border-top: solid 1px var(--color-border);
+        padding: 15px 5px;
+        margin-top: 15px;
+      }
     }
 
     code-block {
@@ -80,7 +101,12 @@
             logo
           })
         }
-        body
+
+        html.main(body)
+
+        if footer != none {
+          html.footer(footer)
+        }
       })
     })
   })