Various tweaks based on design feedback

Tommy sent over some feedback, and I've tried to incorporate it. I've
brought in the Light variant of the Source Serif font, as although
figma uses Regular, these seemed to render too heavy in browsers even
with the smoothing options I also added.

join.html

@@ -37,7 +37,7 @@ layout: default
   <div class="grid">
     <div class="box stack">
       <h3 class="title">More community</h3>
-      <ul>
+      <ul class="services">
         <li>A transparent, friendly group of mission-driven co-op founders and worker-owners</li>
         <li>Monthly online calls</li>
         <li>Twice-yearly in-person gatherings around the UK</li>
@@ -49,7 +49,7 @@ layout: default
     <div class="box stack">
       <h3 class="title">More skills</h3>
 
-      <ul>
+      <ul class="services">
         <li>Develop business skills</li>
         <li>Share challenges of working in the digital/tech sector</li>
         <li>Swap tools, processes and experience</li>
@@ -59,7 +59,7 @@ layout: default
 
     <div class="box stack">
       <h3 class="title">More work</h3>
-      <ul>
+      <ul class="services">
         <li>Strengthen your co-op’s reputation and value proposition by association with CoTech</li>
         <li>Generate leads through the CoTech brand and presence at sector events</li>
         <li>Get referrals from other members</li>