Mention that --wm is needed if wmname has been used

Addresses #40.

README.org

@@ -60,6 +60,8 @@ Old users please note that =-W|--normal-window=, =-z|--sleep-terminal=, and =-Z|
 ** Automatic Window Manager Detection (=-a=)
 =-a= / =--auto-detect-wm= can be specified to automatically set certain options (=-l=, =-L=, =-d=, and/or =-i=) based on the current window manager. These flags (whether automatically or manually set) may be necessary for tdrop to behave correctly (e.g. they are required for =-w=, =-h=, =-x=, and =-y= to work correctly for tiling window managers with floating support). See the manpage for further details about these flags.
 
+Note that if you've used [[https://tools.suckless.org/x/wmname][wmname]] to change your window manager's name, tdrop will use any settings for that name instead. In this case, you will generally need to specify the real name of your window manager using the =--wm= flag in order for =-a= to work correctly (e.g. if you are using bspwm and have run =wmname LG3D=, you will need to specify =--wm bspwm=).
+
 ** Monitor Awareness (=-m=)
  =-m= / =--monitor-aware= can be specified to automatically resize the dropdown based on the current monitor's size when percentages are used for =-w= and/or =-h=. This may be helpful for users of multiple monitors who don't want dropdowns spanning across monitors.
 

tdrop.1

@@ -85,7 +85,7 @@ This option only applies for dropdowns (not auto-hiding and auto-showing). Speci
 .TP
 \fB --wm=NAME\fR
 .TP
-Mimic another WM's rules with -a. This is unlikely to be useful. It could potentially be used in the case where a similar fork of a window manager had a different name. (default: automatically detected)
+Specify the window manager name (which determines the default settings when -a is specified). This may be useful if you've change the name of your window manager using wmname as this will prevent tdrop from correctly detecting the real window manager name. This could also potentially be useful if the all the default -a settings for another window manager work with the current one (e.g. if using a similar but differently named fork of some window manager). (default: automatically detected)
 \fB --class=NAME\fR
 Providing this option lets tdrop know what the class (or classname) of the window is (it does not actually set the class for a window). This is used for window managers like bspwm that use the class for floating rules. For some commonly used programs, tdrop will already use the correct class. This option is useful when the program name and class are not the same and there is not already a default mapping between the two. (default: the program name or a known substitution)