docs(streams): adds docs for streaming files with StreamableFiles

[jmcdo29]

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https://github.com/nestjs/docs.nestjs.com/blob/master/CONTRIBUTING.md

PR Type

What kind of change does this PR introduce?

[ ] Bugfix
[ ] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[X] Docs
[ ] Other... Please describe:

What is the current behavior?

Issue Number: N/A
There's no documentation for a new feature being implemented (nest#5278)

What is the new behavior?

There's now docs showing how files can be streamed back without interfering with the interceptor's post-controller logic.

Does this PR introduce a breaking change?

[ ] Yes
[X] No

Other information

Looks like some of the compiled output from degni got modified. Let me know if you want me to remove that or keep it. Looks like it shouldn't modify the final output to the webpage

[kamilmysliwiec]

Suggested change

	There won't always be a time where you're sending back JSON or string responses. There may be times where you'd like to send back a file from the server to the client. In an express application, you may use something like
	There won't always be a time where you're sending back JSON or string responses. There may be times where you'd like to send back a file from the server to the client. In an express application, you may use something like

Maybe instead of showing an express example here, we could present how it could be accomplished using the standard, Response object (saying it's pretty much the same way as in native express/fastify application). The reason is that we're slowly getting more and more users that are not even familiar with express itself