Add entries in past abilities for access to new abilities

[jemarq04]

Added entries in pokemon_abilities_past.csv for all pokemon that gained additional abilities. This was previously mentioned in PR #1230. (For example, in Gen. 4, Pidgey gained a secondary ability 'Tangled Feet'. In Gen. 3, Pidgey's ability slot 2 was empty.) The only pokemon omitted were pokemon from Unova that gained a hidden ability in Pokemon Black 2/White 2, as this was within the same generation they were introduced.

The information on the abilities was gathered from the following Bulbapedia resources:

• https://bulbapedia.bulbagarden.net/wiki/List_of_modified_Ability_access#Additional_access_to_new_Abilities
• https://bulbapedia.bulbagarden.net/wiki/List_of_Pok%C3%A9mon_with_released_Hidden_Abilities_(Generation_V) (for Hidden Abilities added in Gen. 5)

Two files were modified:

• data/v2/csv/pokemon_abilities_past.csv: Modified to include these entries for pokemon gaining access to new abilities.
• data/v2/build.py: Modified to allow for "null" option for the previous ability. A "null" option will just mean that this pokemon did not previously have an ability in this slot.

[Naramsim]

Hi! Thanks! I understand the logic. We need to document it here: https://github.com/PokeAPI/pokeapi.co/blob/master/src/docs/pokemon.json

[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).

[jemarq04]

Hi! Thanks! I understand the logic. We need to document it here: https://github.com/PokeAPI/pokeapi.co/blob/master/src/docs/pokemon.json

Ah, I had forgotten that this change would need to be documented! Since this PR has already been closed, I should make this change in a separate PR then?
Edit: Never mind, I see now that this is a different repository. I'll add that in - it looks like the "past_abilities" field doesn't even exist in the docs yet!