snapcast: show snapweb placeholder

snapserver has a built-in webserver which is able to host a web player:
snapweb. [1]
It is accessible at http://snapserver:1780/ but with enabled "doc_root"
setting and with missing directory the browser shows an empty page
with a message: "The resource '/' was not found."

Fix this with disabling the "doc_root" setting in "/etc/snapserver.conf"
This "doc_root" was enabled and set to "/usr/share/snapserver/snapweb"
in upstream commit fcbe40585875 ("Install snapweb") [2], back in 2020
and released in v0.21.0 of Snapcast.

This was reported in an upstream discussion by Robert Muth. [3]

[1]: https://github.com/badaix/snapweb
[2]: https://github.com/badaix/snapcast/commit/fcbe405858752457a67006eeff4f0da60e8fbc89
[3]: https://github.com/badaix/snapcast/discussions/1417#discussioncomment-14480178

Fixes: eeb8d131fc ("snapcast: add package snapserver and snapclient")
Signed-off-by: Szabolcs Hubai <szab.hu@gmail.com>

sound/snapcast/Makefile

@@ -4,7 +4,7 @@ include $(TOPDIR)/rules.mk
 
 PKG_NAME:=snapcast
 PKG_VERSION:=0.28.0
-PKG_RELEASE:=1
+PKG_RELEASE:=2
 
 PKG_SOURCE_PROTO:=git
 PKG_SOURCE_URL:=https://github.com/badaix/snapcast.git
@@ -84,9 +84,9 @@ define Package/snapserver/install
 	$(INSTALL_DIR) $(1)/etc/init.d
 	$(INSTALL_BIN) ./files/snapserver.init $(1)/etc/init.d/snapserver
 	$(INSTALL_CONF) $(PKG_BUILD_DIR)/server/etc/snapserver.conf $(1)/etc/snapserver.conf
+	$(SED) 's/.*doc_root *=/#doc_root =/' $(1)/etc/snapserver.conf
 	$(INSTALL_DIR) $(1)/etc/config
 	$(INSTALL_CONF) ./files/snapserver.conf $(1)/etc/config/snapserver
-
 endef
 
 define Package/snapclient/install