Stepper: Add flow title when no pagetitle

[escapemanuele]

Related to #

Proposed Changes

Add a default Create a site page title, similar to what's done in Start here

Why are these changes being made?

To add a page title to the page

Testing Instructions

• Live link
• Visit /setup/onboarding
• Check that the Page title is Create a site
• Visit /setup/sensei and check that it is Course Creator
• Visit /setup/newsletter and check that it is Newsletter

[github-actions]

Calypso Live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-120889

Jetpack Cloud live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-120889&env=jetpack

Automattic for Agencies live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-120889&env=a8c-for-agencies

[matticbot]

This PR modifies the release build for the following Calypso Apps:

For info about this notification, see here: PCYsg-OT6-p2

• notifications
• wpcom-block-editor

To test WordPress.com changes, run install-plugin.sh $pluginSlug stepper-page-title on your sandbox.

[matticbot]

Here is how your PR affects size of JS and CSS bundles shipped to the user's browser:

App Entrypoints (~18 bytes removed 📉 [gzipped])

name           parsed_size           gzip_size
entry-stepper        -41 B  (-0.0%)      -18 B  (-0.0%)

Common code that is always downloaded and parsed every time the app is loaded, no matter which route is used.

Legend

What is parsed and gzip size?

Parsed Size: Uncompressed size of the JS and CSS files. This much code needs to be parsed and stored in memory.
Gzip Size: Compressed size of the JS and CSS files. This much data needs to be downloaded over network.

Generated by performance advisor bot at iscalypsofastyet.com.

[renancarvalho]

LGTM! 👍