Policy templates for Firefox 127 and Firefox ESR 115.12

Note: I strongly recommend reading the enterprise release notes for this version of Firefox since we have a new ESR coming up.

Note: While these templates will work for Firefox ESR 102, they might contain new policies that are not in Firefox ESR 102. If you need to manage Firefox ESR 102, you should use v4.12

I'm no longer using a versioned README for documentation, I'm using a GitHub page which is available at:

https://mozilla.github.io/policy-templates/

You can search on the corresponding version of Firefox (127 in this case) to see version specific policy changes.

If you need to see version specific documentation, you use this link:

https://github.com/mozilla/policy-templates/blob/v5.12/docs/index.md

Note: The changes below only apply to Firefox 127, not to the Firefox 115 ESR.

This release adds the following policies:

DisableEncryptedClientHello - Disable the TLS Feature Encrypted Client Hello (ECH).
PostQuantumKeyAgreementEnabled - Enable post-quantum key agreement for TLS.
HttpsOnlyMode - Configure HTTPS-Only Mode.
HttpAllowlist - Configure origins that will not be upgraded to HTTPS.

This release updates the following policies:

Preferences - The preferences security.mixed_content.block_display_content and security.mixed_content.upgrade_display_content can now be set via policy.
UserMessaging - WhatsNew has been deprecated.
ExtensionSettings - Add support for temporarily_allow_weak_signatures to allow installing extensions signed using deprecated signature algorithms.

For more information about Firefox 127 and Firefox ESR 115.12, see the enterprise release notes.

Thanks to @vossni for their contributions.