When no tasks.json, Run BuildTask gives unhelpful error message

[ramya-rao-a]

Test tour MERN - #22277

Not really MERN specific

• VSCode Version: Insiders
• OS Version: Mac

Steps to Reproduce:

As a new user who stumbled upon tasks, one might get tempted to run Tasks: Run Build Task assuming that VS Code was smart enough to figure out how to build the project.

And they get the below:

Instead we should have a message that asks the user to create tasks.json
or
create one for them and ask them to check it before running the build command
or
if their package.json has a "build" script, use that

[chrmarti]

Tracked with #24146