patch 8.1.1221: filtering does not work when listing marks

Problem:    Filtering does not work when listing marks.
Solution:   Implement filtering marks. (Marcin Szamotulski, closes #3895)
diff --git a/runtime/doc/various.txt b/runtime/doc/various.txt
index 923ac24..8b4f988 100644
--- a/runtime/doc/various.txt
+++ b/runtime/doc/various.txt
@@ -571,17 +571,19 @@
 			the output, not necessarily the whole line. Only some
 			commands support filtering, try it out to check if it
 			works. Some of the commands that support filtering:
-                          |:#|          - filter whole line
-                          |:command|    - filter by command name
-                          |:files|      - filter by file name
-                          |:highlight|  - filter by highlight group
-                          |:jumps|      - filter by file name
-                          |:let|        - filter by variable name
-                          |:list|       - filter whole line
-                          |:llist|      - filter by file name or module name
-                          |:oldfiles|   - filter by file name
-                          |:clist|      - filter by file name or module name
-                          |:set|        - filter by variable name
+			   |:#|          - filter whole line
+			   |:clist|      - filter by file name or module name
+			   |:command|    - filter by command name
+			   |:files|      - filter by file name
+			   |:highlight|  - filter by highlight group
+			   |:jumps|      - filter by file name
+			   |:let|        - filter by variable name
+			   |:list|       - filter whole line
+			   |:llist|      - filter by file name or module name
+			   |:marks|      - filter by text in the current file,
+					   or file name for other files
+			   |:oldfiles|   - filter by file name
+			   |:set|        - filter by variable name
 
 			Only normal messages are filtered, error messages are
 			not.