[Release] v6.15.0

[github-actions]

What's Changed

• Expose EnvHttpProxyAgent to Node.js core bundle, so it can be turned … by @mcollina in Expose EnvHttpProxyAgent to Node.js core bundle, so it can be turned … #3148
• test: add headerslist copy check by @tsctx in test: add headerslist copy check #3156
• chore: ensure automated v6 release compared to v6 by @mweberxyz in chore: ensure automated v6 release compared to v6 #3149
• fetch: do not leak signal listeners by @mcollina in fetch: do not leak signal listeners #3158
• fix: request cache mode is not the same as request mode by @tsibley in fix: request cache mode is not the same as request mode #3151
• fetch: don't re-lowercase HeadersList by @tsctx in fetch: don't re-lowercase HeadersList #3159
• fix casing issue when cloning Headers object by @KhafraDev in fix casing issue when cloning Headers object #3160
• build(deps): bump node from 6d0f18a to db8772d in /build by @dependabot in build(deps): bump node from 6d0f18a to db8772d in /build #3163
• fix header cloning bug by @tsctx in fix header cloning bug #3162
• chore: change bench naming for h2 by @metcoder95 in chore: change bench naming for h2 #3165
• expose WebSocket related events in node bundle by @KhafraDev in expose WebSocket related events in node bundle #3167
• feat: add support for if-match on retry handler by @metcoder95 in feat: add support for if-match on retry handler #3144
• fix: correct firing order of abort events by @tsctx in fix: correct firing order of abort events #3169
• create fast MessageEvent by @KhafraDev in create fast MessageEvent #3170
• chore: add explicitly @fastify/busboy by @Uzlopak in chore: add explicitly @fastify/busboy #3172
• chore: remove sinon as dev dependency by @Uzlopak in chore: remove sinon as dev dependency #3171
• webidl changes by @KhafraDev in webidl changes #3175
• preserve dictionary key name in webidl errors by @KhafraDev in preserve dictionary key name in webidl errors #3176

New Contributors

• @tsibley made their first contribution in fix: request cache mode is not the same as request mode #3151

Full Changelog: v6.14.1...v6.15.0

[mcollina]

lgtm