gh-92626: Correct JavaScript MIME types + extensions per RFC 9239

[mathiasbynens]

This patch updates the MIME type configuration per RFC 9239.
https://www.rfc-editor.org/rfc/rfc9239

First, the recommended MIME type is now text/javascript:

The most widely supported media type in use is text/javascript; all
others are considered historical and obsolete aliases of text/javascript.

Second, the .mjs extension is now explicitly registered:

The .mjs file extension signals that the file represents a JavaScript
module. Execution environments that rely on file extensions to
determine how to process inputs parse .mjs files using the Module
grammar of [ECMA-262].

cpython already had an entry for .mjs (great!), but it was using the obsolete
MIME type.

IANA template: https://www.iana.org/assignments/media-types/text/javascript

Issue: #92626

[ghost]

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[bedevere-bot]

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Please, add it using the blurb_it Web app or the blurb command-line tool.

[arhadthedev]

RFC: 9239
Published: May 2022

6.1.Common JavaScript Media Types
6.1.1. text/javascript

🎉🎉🎉 Finally encoding-aware human-readable text is treated as such (text/*) instead of binary blobs (application/*).

text

Text-only data including any human-readable content, source code, or textual data such as comma-separated value (CSV) formatted data.

application

Any kind of binary data that doesn't fall explicitly into one of the other types; either data that will be executed or interpreted in some way or binary data that requires a specific application or category of application to use. Generic binary data (or binary data whose true type is unknown) is application/octet-stream. Other common examples include application/pdf, application/pkcs8, and application/zip.

-- https://developer.mozilla.org/en-US/docs/Web/HTTP/Basics_of_HTTP/MIME_types

[AA-Turner]

Lib/test/mime.types should maybe be updated, although it seems that file hasn't been substantively updated since 2011:

cpython/Lib/test/mime.types

Line 1217 in cb04a09

# text/javascript obsoleted by application/javascript

Also:

cpython/Tools/wasm/README.md

Lines 213 to 217 in 1f134e9

	AddType application/javascript js
	AddType application/wasm wasm
	<IfModule mod_deflate.c>
	AddOutputFilterByType DEFLATE text/html application/javascript application/wasm

A

[AA-Turner]

@warsaw would we backport something like this? I'm unsure if it would count as a bugfix.

A

[arhadthedev]

It would be great to have this PR merged since it brings stuff to the latest RFC.

[encukou]

This was changed in #97934. Apologies for forgetting this PR.