fix(head): fix broken RSS feed and canonical link URLs (#43)

The Pug attributes for the RSS feed and canonical links used
single-quoted Pug attributes with double-quoted Liquid strings.
When Pug renders to HTML, it converts attributes to double-quote
syntax, causing the inner double quotes to break the attribute
value — resulting in truncated URLs (missing /feed.xml, etc.).

Fix by switching to double-quoted Pug attributes with single-quoted
Liquid strings, matching the working pattern used by the CSS link
on the line above.

Fixes #31

Author: TimeToBuildBob

_includes/head.pug

@@ -8,8 +8,8 @@ head
 
   link(rel='icon', type='image/png', href='/img/logo.png')
   link(rel='stylesheet', href="{{ '/css/main.css' | prepend: site.baseurl }}")
-  link(rel='canonical', href='{{ page.url | replace:"index.html","" | prepend: site.baseurl | prepend: site.url }}')
-  link(rel='alternate', type='application/rss+xml', title='{{ site.title }}', href='{{ "/feed.xml" | prepend: site.baseurl | prepend: site.url }}')
+  link(rel='canonical', href="{{ page.url | replace:'index.html','' | prepend: site.baseurl | prepend: site.url }}")
+  link(rel='alternate', type='application/rss+xml', title='{{ site.title }}', href="{{ '/feed.xml' | prepend: site.baseurl | prepend: site.url }}")
 
   // Bootstrap CSS and JS
   link(rel='stylesheet', href='https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css', integrity='sha384-Gn5384xqQ1aoWXA+058RXPxPg6fy4IWvTNh0E263XmFcJlSAwiGgFAW/dAiS6JXm', crossorigin='anonymous')