…kage-lock.json`)

Since we are using `yarn` to install dependencies, it makes sense to use
`yarn.lock` as the lockfile (and get rid of the unused
`package-lock.json`).

…tories

We have the `scripts/{code,docs}.angularjs.org-firebase/` directories,
which contain the necessary code and config for deploying built files to
the `code-angularjs-org` and `docs-angularjs-org` Firebase projects
respectively.

Previously, some of the files that needed to be deployed to Firebase (or
Google Cloud) were placed outside these directories (e.g. in
`deploy/{code,docs}/`).

Since these files are only used for deploying to Firebase/Google Cloud,
this commit changes the deployment process to instead copy the files
inside the directories. In a subsequent commit, this will allow
simplifying the deployment process, by running it from inside each
directory instead of having to copy the `firebase.json` files to the
repository root (and adjust the paths).

These are the destination directory changes:

| Before       | After                                       |
|--------------|---------------------------------------------|
| deploy/code/ | scripts/code.angularjs.org-firebase/deploy/ |
| deploy/docs/ | scripts/docs.angularjs.org-firebase/deploy/ |

…ng directory

Previously, in order to deploy to Firebase from
`scripts/docs.angularjs.org-firebase/`, we had to copy the
`firebase.json` file to the repository root and adjust the contained
paths accordingly.

By running the `firebase` CLI directly (instead of via `yarn`), we are
able to deploy from `docs.angularjs.org-firebase/` directly. This
simplifies the deployment (and local testing) process and paves the way
for also deploying from `code.angularjs.org-firebase/` in a subsequent
commit.

Previously, we only deployed to Firebase hosting for the
`docs-angularjs-org` Firebase project. This meant that the deployed
functions used an old version of Node.js and started failing once
support was dropped for that version. See angular#17111 for details.

This commit fixes this by ensuring that we deploy to all enabled
Firebase services (currently functions and hosting).

Fixes angular#17111
Fixes angular/angularjs.org#251

Previously, we only deployed the built files to Google Cloud Storage for
the `code-angularjs-org` Firebase project. This meant that the other
Firebase services (such as functions, hosting, storage) were not updated
when we made changes to their source code or configuration.
(This isn't a problem at the moment, since the code/configuration for
these service changes infrequently, but could bite us in the future.)

This commit fixes this by ensuring that we deploy to all enabled
Firebase services (currently functions, hosting and storage).

Previously, when deploying `scripts/{code,docs}.angularjs.org-firebase/`
to Firebase, we explicitly specified the target projects. Since the
project IDs are also specified in the respective `.firebaserc` files,
this was unnecessary (and meant we had multiple places to update if the
IDs changed).

This commit simplifies the process by automatically targeting the
default projects (as configured in the `.firebaserc` files) when
deploying to Firebase in CI.

…angularjs-org`

This commit updates `firebase-admin`, `firebase-functions` and
`firebase-tools` to latest versions to take advantage of the most recent
fixes and improvements.

…sendStoredFile()`

Previously, the `sendStoredFile()` Firebase function used `.split('/')`
to split the request path into segments and later used `path.join()` to
join them back together. This worked fine on *nix based systems, which
use `/` as the path separator. On Windows, however, where `\` is the
path separator, the re-constructed paths could not be retrieved from the
Google Cloud Storage bucket. This prevented the Firebase emulators from
working correctly when testing the function locally on Windows.

This commit fixes the issue by using `.join('/')` to join the path
segments back together.