Markdown file missing syntax highlighting

[adamfrly]

Very small change, I noticed that some of the code blocks are missing syntax highlighting making them harder to read. The biggest example I could find was in docs/advanced_specs.md with:

import luxai_s2
custom_env_cfg = dict()
env = gym.make("LuxAI_S2-v0", collect_stats=False, **custom_env_cfg)
env.reset()

Would simply change to:

import luxai_s2
custom_env_cfg = dict()
env = gym.make("LuxAI_S2-v0", collect_stats=False, **custom_env_cfg)
env.reset()

[StoneT2000]

feel free to make a PR to fix!