patch 8.0.1660: the terminal API "drop" command doesn't support options

Problem:    The terminal API "drop" command doesn't support options.
Solution:   Implement the options.
diff --git a/runtime/doc/terminal.txt b/runtime/doc/terminal.txt
index 54c7e1f..f575c82 100644
--- a/runtime/doc/terminal.txt
+++ b/runtime/doc/terminal.txt
@@ -25,7 +25,7 @@
       MS-Windows			|terminal-ms-windows|
 2. Terminal communication	|terminal-communication|
       Vim to job: term_sendkeys()	|terminal-to-job|
-      Job to Vim: JSON API 		|terminal-api|
+      Job to Vim: JSON API		|terminal-api|
       Using the client-server feature	|terminal-client-server|
 3. Remote testing		|terminal-testing|
 4. Diffing screen dumps		|terminal-diff|
@@ -352,7 +352,7 @@
 can even run Vim in the terminal!  That's used for debugging, see below.
 
 Environment variables are used to pass information to the running job:
-    TERM		name of the terminal, 'term'
+    TERM		name of the terminal, from the 'term' option
     ROWS		number of rows in the terminal initially
     LINES		same as ROWS
     COLUMNS		number of columns in the terminal initially
@@ -443,11 +443,25 @@
 <		Output from `:echo` may be erased by a redraw, use `:echomsg`
 		to be able to see it with `:messages`.
 
-	drop {filename}
+	drop {filename} [options]
 
 		Let Vim open a file, like the `:drop` command.  If {filename}
 		is already open in a window, switch to that window.  Otherwise
 		open a new window to edit {filename}.
+
+		[options] is only used when opening a new window.  If present,
+		it must be a Dict.  Similarly to |++opt|, These entries are recognized:
+		  "ff"		file format: "dos", "mac" or "unix"
+		  "fileformat"	idem
+		  "enc"		overrides 'fileencoding'
+		  "encoding"	idem
+		  "bin"		sets 'binary'
+		  "binary"	idem
+		  "nobin"	resets 'binary'
+		  "nobinary"	idem
+		  "bad"		specifies behavior for bad characters, see
+				|++bad|
+
 		Example in JSON: >
 			["drop", "path/file.txt", {"ff": "dos"}]