plugins/rtmp-services: Add ピキ日記 (PikiDiary) as a service

[isoionone]

Description

This PR adds ピキ日記 (PikiDiary), a microblogging platform with a NicoNico-style live streaming feature, to the built-in services list (plugins/rtmp-services/data/services.json) using the WHIP/WebRTC protocol.

It sets the platform's ingest endpoint, links to the user streaming studio dashboard, and includes community-established recommended encoding presets (720p30, H.264, CBR 1600 Kbps, Opus 96 Kbps).

Motivation and Context

PikiDiary is a microblogging site featuring live streaming capabilities. Adding PikiDiary as a native WHIP service in OBS Studio simplifies the onboarding process for the community members, eliminating the need for them to manually configure "Custom..." WHIP servers and settings.

How Has This Been Tested?

• Environment: Tested on OBS Studio 32.1.2 (Windows 11).
• Test Case: Verified that selecting "PikiDiary" from the services dropdown successfully loads the WHIP configuration.
• Stream Test: I generated a bearer token through https://piki.lol/live/studio, initiated the stream from OBS, and successfully negotiated the WebRTC handshake to ingest video/audio onto the live site without errors.

Types of changes

• New feature, non-breaking change which adds functionality

Checklist:

• I have read the contributing document.
• My code has been run through clang-format.
• My code follows the project's style guidelines
• My code is not on the master branch.
• My code has been tested.
• All commit messages are properly formatted and commits squashed where appropriate.
• I have included updates to all appropriate documentation.