feat: add script to install packages locally in a DXP checkout

This is a crude script that will almost certainly have to be evolved as
the shape and structure of the monorepo evolves, but it works for now
with the set of packages that we currently have.

It addresses a bunch of "gotchas" that come with trying to test out
packages with local changes in a liferay-portal checkout. Depending on
which packages you want to test and the dependency graph between them,
you may find that `yarn link` (or even `yarn add`) doesn't do what you
want. Even if you manually copy files (`cp`), things still might not
work because Gradle may decide to re-run a task that ends up blowing
away any changes you make locally under `node_modules`.

At least for the simple case, this script was good enough to allow me to
test:

    #97

even though it involved changes to both `eslint-config` and
`npm-scripts`.

As you can see, it does three things:

- Blows away nested `node_modules` folders inside the monorepo, because
  `yarn add` can end up copying these over in ways that cause confusion
  (broken `bin` links and so on).
- Cleans out the existing versions of the dependencies (in my testing,
  removing and then re-adding seemed to produce a cleaner result than
  just overwriting).
- Adds the modules to be tested.

Like I said at the start, this is a hack (and not even trying to make it
work on Windows), but it's a useful hack.

support/install-packages.sh

@@ -0,0 +1,67 @@
+#!/bin/bash
+#
+# SPDX-FileCopyrightText: © 2020 Liferay, Inc. <https://liferay.com>
+# SPDX-License-Identifier: MIT
+
+##
+#
+# A hacky script to overwrite liferay-frontend-projects packages in a
+# liferay-repo checkout with the ones from this repo, for testing purposes.
+#
+# Usage:
+#
+#     bash install-packages.sh $PATH_TO_PORTAL_REPO
+
+die() {
+  echo "error: $*"
+  exit 1
+}
+
+remove() {
+  while (( "$#" )); do
+    local DEP=$1
+
+    if grep "\"$DEP\"" package.json &> /dev/null; then
+      echo "Removing $DEP dependency"
+      yarn remove -W --silent "$DEP"
+    fi
+
+    shift
+  done
+}
+
+#
+# Main.
+#
+
+ROOT=$(realpath "${BASH_SOURCE%/*}/..")
+
+if [ $# != 1 ]; then
+  echo "Usage: $0 PORTAL_REPO"
+  exit 1
+fi
+
+PORTAL_REPO=$1
+MODULES="${PORTAL_REPO}/modules"
+
+if [ ! -d "$MODULES" -o ! -e "$MODULES/yarn.lock" ]; then
+  die "\`$PORTAL_REPO\` does not appear to be a liferay-portal checkout"
+fi
+
+echo "Purging nested node_modules folders"
+
+find "$ROOT/projects" -depth -name node_modules -print -exec rm -r {} \;
+
+cd "$MODULES"
+
+remove \
+    @liferay/npm-scripts \
+    @liferay/eslint-config \
+    liferay-npm-scripts \
+    eslint-config-liferay
+
+echo "Adding local dependencies"
+
+yarn add -W --dev --silent \
+  "$ROOT/projects/eslint-config" \
+  "$ROOT/projects/npm-tools/packages/npm-scripts"