Add some doc to the github actions / CI scripts (#8034)

* Add some doc to the githuib actions / CI scripts

Type: task

* alalytics-events is more name matching

scripts/ci/Dockerfile

@@ -1,3 +1,5 @@
+# Docker file for end-to-end tests
+
 # Update on docker hub with the following commands in the directory of this file:
 # If you're on linux amd64
 #   docker build -t vectorim/element-web-ci-e2etests-env:latest .

scripts/ci/install-deps.sh

@@ -1,5 +1,12 @@
 #!/bin/bash
 
+# This installs other Matrix dependencies that are often
+# developed in parallel with react-sdk, using fetchdep.sh
+# for branch matching.
+# This will set up a working react-sdk environment, so is
+# used for running react-sdk standalone tests. To set up a
+# build of element-web, use layered.sh
+
 set -ex
 
 scripts/fetchdep.sh matrix-org matrix-js-sdk

scripts/ci/layered.sh

@@ -1,7 +1,9 @@
 #!/bin/bash
 
 # Creates a layered environment with the full repo for the app and SDKs cloned
-# and linked.
+# and linked. This gives an element-web dev environment ready to build with
+# the current react-sdk branch and any matching branches of react-sdk's dependencies
+# so that changes can be tested in element-web.
 
 # Note that this style is different from the recommended developer setup: this
 # file nests js-sdk and element-web inside react-sdk, while the local
@@ -16,7 +18,8 @@ yarn link
 yarn install --pure-lockfile
 popd
 
-# Set up the js-sdk first
+# Also set up matrix-analytics-events so we get the latest from
+# the main branch or a branch with matching name
 scripts/fetchdep.sh matrix-org matrix-analytics-events main
 pushd matrix-analytics-events
 yarn link