patch 8.2.0802: libvterm code lags behind the upstream version

Problem:    Libvterm code lags behind the upstream version.
Solution:   Include revisions 759 - 762.
diff --git a/src/libvterm/doc/seqs.txt b/src/libvterm/doc/seqs.txt
index c03fa51..aa15fec 100644
--- a/src/libvterm/doc/seqs.txt
+++ b/src/libvterm/doc/seqs.txt
@@ -170,6 +170,7 @@
       SGR 4:x          = Underline style
 123   SGR 5            = Blink on
 123   SGR 7            = Reverse on
+      SGR 8            = Conceal on
       SGR 9            = Strikethrough on
       SGR 10-19        = Select font
       SGR 21           = Underline double
@@ -178,6 +179,7 @@
  23   SGR 24           = Underline off
  23   SGR 25           = Blink off
  23   SGR 27           = Reverse off
+      SGR 28           = Conceal off
       SGR 29           = Strikethrough off
       SGR 30-37        = Foreground ANSI
       SGR 38           = Foreground alternative palette