docs: document the reverse proxying options in tinyproxy.conf(5)

docs/man5/tinyproxy.conf.txt.in

@@ -276,6 +276,39 @@ The possible keywords and their descriptions are as follows:
     ports are allowed. To disable CONNECT altogether, include a
     single ConnectPort line with a value of `0`.
 
+*ReversePath*::
+
+    Configure one or more ReversePath directives to enable reverse proxy
+    support. With reverse proxying it's possible to make a number of
+    sites appear as if they were part of a single site.
+
+    If you uncomment the following two directives and run tinyproxy
+    on your own computer at port 8888, you can access example.com,
+    using http://localhost:8888/example/.
+
+    ReversePath "/example/" "http://www.example.com/"
+
+*ReverseOnly*::
+
+    When using tinyproxy as a reverse proxy, it is STRONGLY
+    recommended that the normal proxy is turned off by setting
+    this boolean option to `Yes`.
+
+*ReverseMagic*::
+
+    Setting this option to `Yes`, makes Tinyproxy use a cookie to
+    track reverse proxy mappings. If you need to reverse proxy
+    sites which have absolute links you must use this option.
+
+*ReverseBaseURL*::
+
+    The URL that is used to access this reverse proxy. The URL is
+    used to rewrite HTTP redirects so that they won't escape the
+    proxy. If you have a chain of reverse proxies, you'll need to
+    put the outermost URL here (the address which the end user
+    types into his/her browser).  If this option is not set then
+    no rewriting of redirects occurs.
+
 
 BUGS
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