patch 9.0.1671: Termdebug: error with more than 99 breakpoints

Problem:    Termdebug: error with more than 99 breakpoints.
Solution:   Use a different sign for breakpoint 100 and over. (closes #12589,
            closes #12588)
diff --git a/runtime/doc/terminal.txt b/runtime/doc/terminal.txt
index 7a82fcf..f035704 100644
--- a/runtime/doc/terminal.txt
+++ b/runtime/doc/terminal.txt
@@ -1,4 +1,4 @@
-*terminal.txt*	For Vim version 9.0.  Last change: 2023 Jun 09
+*terminal.txt*	For Vim version 9.0.  Last change: 2023 Jun 28
 
 
 		  VIM REFERENCE MANUAL	  by Bram Moolenaar
@@ -1541,6 +1541,20 @@
 	let g:termdebug_popup = 0
 
 
+Change default signs ~
+							*termdebug_signs*
+Termdebug uses the last two characters of the breakpoint ID in the
+signcolumn to represent breakpoints. For example, breakpoint ID 133
+will be displayed as `33`.
+
+If you want to customize the breakpoint signs: >
+	let g:termdebug_config['sign'] = '>>'
+If there is no g:terminal_config yet you can use: >
+	let g:termdebug_config = {'sign': '>>'}
+
+After this, breakpoints will be displayed as `>>` in the signcolumn.
+
+
 Window toolbar ~
 							*termdebug_winbar*
 By default the Termdebug plugin creates a window toolbar if the mouse is