Add contact information to README

It looks nicer and it’s likely better to use a larger minibuffer in
another frame if needed.

README.org

@@ -96,6 +96,10 @@ Some customization examples:
                                          (internal-border-width . 20))))
   #+end_src
 
------
+* Contact
 
-/To Petr./
+pip-frame.el is available at [[https://git.zamazal.org/pdm/pip-frame][git.zamazal.org]].  You can file issues
+there.
+
+If you don’t want to discuss things publicly or to bother registering
+at yet another web site, you can reach me at [[mailto:pdm@zamazal.org][pdm@zamazal.org]].

pip-frame.el

@@ -49,7 +49,8 @@ Usually, the value should be larger than 0 and much smaller than 1."
 
 (defcustom pip-frame-parameters
   '((left . 0.9)
-    (top .  0.9))
+    (top .  0.9)
+    (minibuffer . nil))
   "Alist of frame parameters to use for the PIP frame.
 The frame size is determined automatically using `pip-frame-scale'
 custom option but it can be overriden here."