Adds "Launching a Compose activity" article

[craiglabenz]

Presubmit checklist

• This PR is marked as draft with an explanation if not meant to land until a future stable release.
• This PR doesn’t contain automatically generated corrections (Grammarly or similar).
• This PR follows the Google Developer Documentation Style Guidelines — for example, it doesn’t use i.e. or e.g., and it avoids I and we (first person).
• This PR uses semantic line breaks of 80 characters or fewer.

[craiglabenz]

Extra fiddling with the website's actual build mechanics may be required, but I haven't ever used the new system so I'm not sure. This is just the raw content for our new article.

[flutter-website-bot]

Visit the preview URL for this PR (updated for commit 72c4c5f):

https://flutter-docs-prod--pr11219-compose-activity-docs-t1pgdlom.web.app

[craiglabenz]

There seems to a small gap in documentation around the excerpter package. When attempting to run the site, I am seeing this error:

$ ./dash_site serve                  
Verifying npm dependencies are up to date...
Resolving dependencies in `/Users/craiglabenz/Dev/git/flutter/website`... 
Because every version of flutter_site from path depends on excerpter from path which doesn't exist (could not find package excerpter at "site-shared/packages/excerpter"), flutter_site from path
  is forbidden.
So, because docs_flutter_dev depends on flutter_site from path, version solving failed.

Is there a specific way to install that package?

[parlough]

@craiglabenz You might be missing the site-shared submodule. Can you try reinitializing it?

git submodule update --init --recursive

Then run dart pub get from the root directory:

dart pub get
./dash_site serve

[sfshaza2]

Some nits. Overall, it's looking good!

[jwill]

Good progress, but...
Consider expanding the top level paragraph describing the approximate flow of what needs to be done with a bit more detail...or extra credit a diagram as well. As currently written, it feels like it jumps into on the dart side/on the android side.

I might think about adding links to things associated with platform methods, or the tutorial page if one exists.

[craiglabenz]

Thanks, @parlough! It didn't occur to me that I might be missing a submodule - but I'd originally cloned this repo ages ago, so I was.

Local development is working for me now :)

[sfshaza2]

@craiglabenz, if you look at the CI detailed results of running "Test", the template has a problem:

Error: There were errors when updating excerpts!
Error: Process completed with exit code 1.
Error: The step failed and an error occurred when attempting to determine whether to continue on error.
Error: The template is not valid. .github/workflows/test.yml (Line: 70, Col: 28): Unexpected value ''

[craiglabenz]

This looks ready for final review from a codeowner, @parlough 😄

[sfshaza2]

lgtm. But am also leaving for either @parlough or @ewindmill (on deck this week) to review.

[ericwindmill]

LGTM

[sfshaza2]

I'm confused. How does this overlap with this: #11232 ?

[jwill]

#11219 and #11232 do not overlap.

[sfshaza2]

You are right. I realize that now. I really dug into this late last week. Thanks again.