Change source hosting link after move to GitHub pages

We didn't commit the release tarballs to the Git repository, so the move
from MIT scripts to GitHub broke this link. The SHA-256 remains unchanged
from the original 2022 release announcement.

Fixes #75

index.html

@@ -419,7 +419,7 @@ <h2>Building from source</h2>
       <div class="row-fluid">
         <div class="span6">
           <h3 class="callout">Latest release</h3><br>
-            <p>Extract <a href="//mosh.org/mosh-1.4.0.tar.gz">mosh-1.4.0.tar.gz</a>, then</p>
+            <p>Extract <a href="https://github.com/mobile-shell/mosh/releases/download/mosh-1.4.0/mosh-1.4.0.tar.gz">mosh-1.4.0.tar.gz</a> (SHA-256 in <a href="mosh-1.4.0-released.html">signed release announcement</a>), then</p>
     <pre>$ cd mosh-1.4.0
 $ ./configure
 $ make

mosh-1.4.0-released.html

@@ -73,7 +73,7 @@ <h1>[mosh-users] mosh 1.4.0 released</h1>
 - -    Use HAVE_UTEMPTER instead of HAVE_UPTEMPTER (Michael Jarvis)
 - -    Apply latest consecutive resize, not earliest (Peter Edwards)
 - -    Use CLOCK_MONOTONIC_RAW when available (Harry Sintonen)
-- -    Add tmux and alacritty to title_term_types (Naïm Favier)
+- -    Add tmux and alacritty to title_term_types (Na&iuml;m Favier)
 - -    Don't sometimes hang just after launching ssh (Kalle Samuels)
 
 Internal changes: