Add "education" virtual category to Porter's Handbook.

- The category itself was added to the ports framework in r555738.
- While there, fix a typo.

PR:		248403
Submitted by:	PauAmma <pauamma@gundo.com>
Reviewed by:	adamw, bcr, mat
Differential Revision:	https://reviews.freebsd.org/D27340

en_US.ISO8859-1/books/porters-handbook/makefiles/chapter.xml

@@ -1126,6 +1126,18 @@ PORTEPOCH=	1</programlisting>
 		category.</entry>
 	    </row>
 
+	    <row>
+	      <entry><filename>education</filename>
+		<literal>*</literal></entry>
+	      <entry>Education-related software.</entry>
+	      <entry>This includes applications, utilities, or games
+		primarily or substantially designed to help the user
+		learn a specific topic or study in general.  It also
+		includes course-writing applications, course-delivery
+		applications, and classroom or school management
+		applications.</entry>
+	    </row>
+
 	    <row>
 	      <entry><filename>elisp</filename>
 		<literal>*</literal></entry>
@@ -1786,7 +1798,7 @@ PORTEPOCH=	1</programlisting>
 	not have a corresponding subdirectory in the ports tree&mdash;
 	or <emphasis>physical</emphasis> categories&mdash;those that
 	do.  This section discusses the issues involved in creating a
-	new physical category.  Read it thouroughly before proposing a
+	new physical category.  Read it thoroughly before proposing a
 	new one.</para>
 
       <para>Our existing practice has been to avoid creating a new