docs: improve metatags in doxygen

tools/doxygen_plugins.lua

@@ -13,11 +13,31 @@ local plugin_paragraph_link = '<script type="text/javascript" src="$relpath^doxy
 local header_file = io.open('doxygen/header.html', 'r')
 local header_content = header_file:read('*a')
 
+local icon_clipboard = '<!--END PROJECT_ICON-->\n'
+local icon_clipboard_pattern = '<%!%-%-END PROJECT_ICON%-%->'
+local plugin_metadata = [[
+<meta name="title" content="$projectname Docs"/>
+<meta name="summary" content="$projectbrief"/>
+<meta name="description" content="$title"/>
+
+<meta property="og:type" content="website"/>
+<meta property="og:title" content="$projectname Docs"/>
+<meta property="og:site_name" content="$projectbrief"/>
+<meta property="og:description" content="$title"/>
+<meta property="og:image" content="http://docs.gamely.com.br/icon80x80.png"/>
+
+<meta property="twitter:card" content="summary_large_image"/>
+<meta property="twitter:title" content="$projectname Docs"/>
+<meta property="twitter:description" content="$title"/>
+<meta property="twitter:image" content="http://docs.gamely.com.br/icon80x80.png"/>
+]]
+
 header_file:close()
 
 header_file = io.open('doxygen/header.html', 'w')
 header_content = header_content:gsub(copy_clipboard_pattern, text_clipboard..plugin_paragraph_link)
 header_content = header_content:gsub(copy_clipboard_pattern, text_clipboard..plugin_toggle_darkmode)
+header_content = header_content:gsub(icon_clipboard_pattern, icon_clipboard..plugin_metadata)
 
 header_file:write(header_content)
 header_file:close()