Typo fixes in CONTRIBUTING.md

Typo fixes as well as updating it to no longer refer to twitter but
rather mastodon.

CONTRIBUTING.md

@@ -5,12 +5,13 @@
 0. Verify that the <A HREF="https://www.ioccc.org/index.html#enter">IOCCC is open</A> for submissions.
 1. If the IOCCC is open, you need to register as a contestant.
 See: <A HREF="https://www.ioccc.org/index.html#enter">how to enter</A> for how to register.
-2. Once you have been registered, you will receive and Email message for how prepair your entries for submission,
+2. Once you have been registered, you will receive and Email message for how to
+prepare your entries for submission,
 and how to upload the compressed tarballs to our submission portal.
 3. Once the <A HREF="https://www.ioccc.org/index.html#enter">IOCCC</A> closes,
 the judges will select the <A HREF="https://www.ioccc.org/years.html">winning entries</A>,
-announce them on the <A HREF="https://twitter.com/ioccc">@IOCCC twitter feed</A>,
-notify the winners via Email using their previouslt registered Email address,
+announce them on the <A HREF="https://fosstodon.org/@ioccc">@IOCCC mastodon feed</A>,
+notify the winners via Email using their previously registered Email address,
 and upload the winning code to the <A HREF="https://github.com/ioccc-src/winner">ioccc-src/winner</A> repo
 which in turn will cause them to be displayed on the  <A HREF="https://www.ioccc.org/years.html">IOCCC winners page</A>.