Add Gen IV Headbutt encounters

[Machine-Maker]

Change description

Adds headbutt encounters for HG/SS in Gen IV.

I took the headbutt.json file from decompiled source for all the encounters and location. Claude helped come up with a mapping from location to location within pokeapi.

AI coding assistance disclosure

Claude Code helped me understand encounter mechanics by analyzing decompiled source for HG game.

Contributor check list

• I have written a description of the contribution and explained its motivation.
• I have written tests for my code changes (if applicable).
• I have read and understood the AI Assisted Contribution guidelines.
• I will own this change in production, and I am prepared to fix any bugs caused by my code change.

Closes #419

[Machine-Maker]

Ok, PR is updated with latest changes on master.

[jemarq04]

A few quick comments. I'll take a look at specific encounter data more in-depth after we've discussed these

[jemarq04]

Checked a few files and they look great, so I'll assume the rest is looking good. Thanks again for the contributions!

[pokeapi-machine-user]

A PokeAPI/api-data refresh has started. In ~45 minutes the staging branch of PokeAPI/api-data will be pushed with the new generated data.

The staging branch will be deployed in our staging environment and the entire API will be ready to review.

A Pull Request (master<-staging) will be also created at PokeAPI/api-data and assigned to the PokeAPI Core team to be reviewed. If approved and merged new data will soon be available worldwide at pokeapi.co.

[pokeapi-machine-user]

The updater script has finished its job and has now opened a Pull Request towards PokeAPI/api-data with the updated data.

The Pull Request can be seen deployed in our staging environment when CircleCI deploy will be finished (check the start time of the last build).