unicode: upgrade to Unicode 13.0.0

Fixes #40755

Change-Id: I14b3977317994095db8ae1bd873c174641209356
Reviewed-on: https://go-review.googlesource.com/c/go/+/248765
Run-TryBot: Marcel van Lohuizen <mpvl@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

api/except.txt

@@ -456,3 +456,4 @@ pkg syscall (freebsd-arm-cgo), type Statfs_t struct, Mntonname [88]int8
 pkg text/scanner, const GoTokens = 1012
 pkg unicode, const Version = "10.0.0"
 pkg unicode, const Version = "11.0.0"
+pkg unicode, const Version = "12.0.0"

api/next.txt

@@ -0,0 +1,5 @@
+pkg unicode, const Version = "13.0.0"
+pkg unicode, var Chorasmian *RangeTable
+pkg unicode, var Dives_Akuru *RangeTable
+pkg unicode, var Khitan_Small_Script *RangeTable
+pkg unicode, var Yezidi *RangeTable

doc/go1.16.html

@@ -90,6 +90,17 @@ <h2 id="library">Core library</h2>
   TODO
 </p>
 
+<h3 id="unicode"><a href="/pkg/unicode/">unicode</a></h3>
+
+<p><!-- CL 248765 -->
+  The <a href="/pkg/unicode/"><code>unicode</code></a> package and associated
+  support throughout the system has been upgraded from Unicode 12.0.0 to
+  <a href="https://www.unicode.org/versions/Unicode13.0.0/">Unicode 13.0.0</a>,
+  which adds 5,930 new characters, including four new scripts, and 55 new emoji.
+  Unicode 13.0.0 also designates plane 3 (U+30000-U+3FFFF) as the tertiary
+  ideographic plane.
+</p>
+
 <h3 id="minor_library_changes">Minor changes to the library</h3>
 
 <p>