tinyproxy: reverse proxy config options are not being parsed

Maintainer: @jow-
Environment: MIPS - Xiaomi Mi Router 4C - OpenWRT 21.02

Description: TinyProxy supports reverse proxy but the OpenWRT config file for it does not recognize related fields when generating TinyProxy config file under /tmp/etc.

Reverse-proxy related fields:

# 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 Google using
# http://localhost:8888/google/ and Wired News using
# http://localhost:8888/wired/news/. Neither will actually work
# until you uncomment ReverseMagic as they use absolute linking.
#
#ReversePath "/google/"	"http://www.google.com/"
#ReversePath "/wired/"	"http://www.wired.com/"

#
# When using tinyproxy as a reverse proxy, it is STRONGLY recommended
# that the normal proxy is turned off by uncommenting the next directive.
#
#ReverseOnly Yes

#
# Use a cookie to track reverse proxy mappings. If you need to reverse
# proxy sites which have absolute links you must uncomment this.
#
#ReverseMagic Yes

#
# The URL that's 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 not set then no rewriting occurs.
#
#ReverseBaseURL "http://localhost:8888/"

Above text taken from official GitHub repo of TinyProxy.

Start by tracing the OpenWrt configuration path that generates TinyProxy's file under /tmp/etc, then compare its recognized options with ReversePath, ReverseOnly, ReverseMagic, and ReverseBaseURL. Confirm that configured values appear in the generated file, and add a focused regression check if the package's existing test structure provides one.