docs: add instructions specifically for addons.mozilla.org reviewers

doc/DEVELOPMENT.org

@@ -88,7 +88,7 @@ You need go to https://addons.mozilla.org/en-GB/developers/addon/promnesia/versi
 
 Sometimes it may be flagged for a review, so you'll need to upload source code.
 You can use =git archive master --output=promnesia-source.zip= if you're asked for it.
-For build instructions, you can point the reviewers at =https://github.com/karlicoss/promnesia/blob/master/doc/DEVELOPMENT.org#build-extension= or/and the github actions config.
+For build instructions, you can point the reviewers at [[file:addons-mozilla-org.org][these instructions]], =https://github.com/karlicoss/promnesia/blob/master/doc/DEVELOPMENT.org#build-extension= or/and the github actions config.
 
 ** CWS (chrome web store)
 : cd extension

doc/addons-mozilla-org.org

@@ -0,0 +1,29 @@
+To build the addon (expects Ubuntu 18.04/bionic at the moment):
+
+#+begin_src
+$ sudo apt update && sudo apt install -y git curl
+$ curl -fsSL https://deb.nodesource.com/setup_16.x | sudo -E bash -
+$ sudo apt install -y nodejs
+$ git clone https://github.com/karlicoss/promnesia.git
+$ cd promnesia/extension/
+$ npm install
+$ ./build --firefox --release --lint
+#+end_src
+
+# TODO: how to keep the instructions consistent with the CI?
+
+The final artifact will be in =extension/dist/firefox/web-ext-artifacts/promnesia-<version>.zip=
+
+NOTE: the easiest ways to test the above instructions in Docker would be
+
+#+begin_src
+# run the container
+docker run -it ubuntu:bionic /bin/bash
+
+# inside the container
+$ sudo apt update && sudo apt install -y sudo
+
+# and after that run the same commands as above.
+
+#+end_src
+