README.md: tell windows user to read docs instead of taking random guesses

Windows users do not understand "just place the script into your $PATH",
but surprisingly decide that means they should take random guesses as to
what that means instead of reading the linked page that explains it in
more detail...and then complain that it was hard to figure out.

Make it clear that if they don't understand that statement, they also
should read the more detailed explanation page.

Signed-off-by: Elijah Newren <newren@gmail.com>

README.md

@@ -44,18 +44,22 @@ filter-repo requires:
 
 # How do I install it?
 
-git-filter-repo is a single-file python script, which was done to make
-installation for basic use on many systems trivial: just place the
-script into your $PATH.
+`git-filter-repo` is a single-file python script, which was done to make
+installation for basic use on many systems trivial: just place that
+file into your $PATH.
 
 See [INSTALL.md](INSTALL.md) for things beyond basic usage or special
-cases.  The more involved instructions are only needed if you
-
-  * are working with a python3 executable named something other than "python3"
-  * want to install documentation (beyond the builtin docs shown with -h)
-  * want to run some of the [contrib](contrib/filter-repo-demos/) examples
-  * want to create your own python filtering scripts using filter-repo as a
-    module/library
+cases.  The more involved instructions are only needed if one of the
+following apply:
+
+  * you do not find the above comment about trivial installation intuitively
+    obvious
+  * you are working with a python3 executable named something other than
+    "python3"
+  * you want to install documentation (beyond the builtin docs shown with -h)
+  * you want to run some of the [contrib](contrib/filter-repo-demos/) examples
+  * you want to create your own python filtering scripts using filter-repo as
+    a module/library
 
 # How do I use it?