[docs] improvements to offline, PWA, and service worker guides

[gillkyle]

Description

While working on the workflow for users building apps with Gatsby (#18993) I encountered this last portion of docs that could use some fine-tuning. Since a lot of this information is located in different places like plugin READMEs, blog posts, and guides, it would make sense to consolidate it all in a little more streamlined of an approach in the guides that exist.

Notes of possible improvements

Some notes that I have from that issue and that I saw reviewing those docs that could lead to some wins:

• transfer content from the "Gatsby for Apps" post to guides which has content on PWA's including service workers and the app shell model that Gatsby follows
• link to /packages/gatsby-plugin-offline instead of npm in guides like this one to keep users on .org
• update the guides on service workers with more steps from the plugin README that describes newer configuration options
  • the current guide says "You can add a custom service worker if your use case requires something that gatsby-plugin-offline doesn’t support.", though it looks like the offline plugin supports appending code to the service worker to extend it's functionality so distinguishing between adding a default service worker with the offline plugin, extending the default plugin, or just using your own service worker seems like it would help
• add information about pulling in app data quickly using service workers so you don't have to wait on the network (this would be awesome if it included an example of an app with a logged in user using a service worker)

this issue is to capture the last bits of improvements of the gatsby for apps workflow so we can close the meta issue that has been tracking that work

[marcysutton]

I'm opening this up to the community; if anyone wants to work on it let us know!

[github-actions[bot]]

Hiya!

This issue has gone quiet. Spooky quiet. 👻

We get a lot of issues, so we currently close issues after 30 days of inactivity. It’s been at least 20 days since the last update here.
If we missed this issue or if you want to keep it open, please reply here. You can also add the label "not stale" to keep this issue open!
As a friendly reminder: the best way to see this issue, or any other, fixed is to open a Pull Request. Check out gatsby.dev/contribute for more information about opening PRs, triaging issues, and contributing!

Thanks for being a part of the Gatsby community! 💪💜

[github-actions[bot]]

Hiya!

This issue has gone quiet. Spooky quiet. 👻

We get a lot of issues, so we currently close issues after 30 days of inactivity. It’s been at least 20 days since the last update here.
If we missed this issue or if you want to keep it open, please reply here. You can also add the label "not stale" to keep this issue open!
As a friendly reminder: the best way to see this issue, or any other, fixed is to open a Pull Request. Check out gatsby.dev/contribute for more information about opening PRs, triaging issues, and contributing!

Thanks for being a part of the Gatsby community! 💪💜

[github-actions[bot]]

Hiya!

This issue has gone quiet. Spooky quiet. 👻

We get a lot of issues, so we currently close issues after 30 days of inactivity. It’s been at least 20 days since the last update here.
If we missed this issue or if you want to keep it open, please reply here. You can also add the label "not stale" to keep this issue open!
As a friendly reminder: the best way to see this issue, or any other, fixed is to open a Pull Request. Check out gatsby.dev/contribute for more information about opening PRs, triaging issues, and contributing!

Thanks for being a part of the Gatsby community! 💪💜

[github-actions[bot]]

Hey again!

It’s been 30 days since anything happened on this issue, so our friendly neighborhood robot (that’s me!) is going to close it.
Please keep in mind that I’m only a robot, so if I’ve closed this issue in error, I’m HUMAN_EMOTION_SORRY. Please feel free to reopen this issue or create a new one if you need anything else.
As a friendly reminder: the best way to see this issue, or any other, fixed is to open a Pull Request. Check out gatsby.dev/contribute for more information about opening PRs, triaging issues, and contributing!

Thanks again for being part of the Gatsby community! 💪💜