patch 9.1.0443: Can't use blockwise selection with width for getregion()

Problem:  Can't use a blockwise selection with a width for getregion().
Solution: Add support for blockwise selection with width like the return
          value of getregtype() or the "regtype" value of TextYankPost
          (zeertzjq).

closes: #14842

Signed-off-by: zeertzjq <zeertzjq@outlook.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/runtime/doc/builtin.txt b/runtime/doc/builtin.txt
index afd84c1..866fab1 100644
--- a/runtime/doc/builtin.txt
+++ b/runtime/doc/builtin.txt
@@ -4288,14 +4288,13 @@
 		The optional argument {opts} is a Dict and supports the
 		following items:
 
-			type		Specify the region's selection type
-					(default: "v"):
-			    "v"		for |characterwise| mode
-			    "V"		for |linewise| mode
-			    "<CTRL-V>"	for |blockwise-visual| mode
+			type		Specify the region's selection type.
+					See |getregtype()| for possible values,
+					except it cannot be an empty string.
+					(default: "v")
 
 			exclusive	If |TRUE|, use exclusive selection
-					for the end position
+					for the end position.
 					(default: follow 'selection')
 
 		You can get the last selection type by |visualmode()|.