Record pinned bedrock and deepslate blockstates in CHANGELOG

[BharathASL]

Follow-up from the final review of #232. That PR pinned the bedrock, deepslate and infested_deepslate blockstates on main (pack_template/assets/minecraft/blockstates/{bedrock,deepslate,infested_deepslate}.json), but CHANGELOG.md [Unreleased] has no entry for it. Players will see the change, and the equivalent stone override is recorded at CHANGELOG.md:L44-L46.

What to do

• Add a line under [Unreleased] → ### Added (CHANGELOG.md:L15) for the pinned blockstates. bedrock now uses a single un-rotated variant. deepslate and infested_deepslate drop the random mirrored and y: 180 variants but keep the per-axis pillar rotation (axis=x: x: 90, y: 90; axis=z: x: 90). Reference feat(blockstates): pin un-rotated bedrock and deepslate variants #232.
• When Pin un-rotated infested_stone variants to match stone.json #236 lands, extend the same line (or add one) for infested_stone.

Acceptance criteria

• CHANGELOG.md [Unreleased] records the pinned bedrock, deepslate and infested deepslate blockstates and says that deepslate keeps its axis rotation.