install-by-deb: Add note for debian packages

Signed-off-by: Masahiro Nakagawa <repeatedly@gmail.com>

Author: repeatedly

install/install-by-deb.md

@@ -30,9 +30,12 @@ your OS properly. This will prevent many unnecessary problems.
 
 For Ubuntu, we currently support "Ubuntu 18.04 LTS / Bionic 64bit",
 "Ubuntu 16.04 LTS / Xenial 64bit", "Ubuntu 14.04 LTS / Trusty 64bit".
-For Debian, we currently support "Debian 10 Buster 64bit", "Debian 9 Stretch 64bit",
+For Debian, we currently provide "Debian 10 Buster 64bit", "Debian 9 Stretch 64bit",
 "Debian 8 Jessie 64bit".
 
+Note: treasure data doesn't verify debian packages. If you have a problem with debian packages,
+send a patch to [omnibus-td-agent repository](https://github.com/treasure-data/omnibus-td-agent).
+
 A shell script is provided to automate the installation process for each
 version. The shell script registers a new apt repository at
 `/etc/apt/sources.list.d/treasure-data.list` and installs the `td-agent`