chore(release): 1.0.0-alpha.18 [skip ci]

# [1.0.0-alpha.18](https://code.podlibre.org/podlibre/castopod/compare/v1.0.0-alpha.17...v1.0.0-alpha.18) (2020-11-09)

### Features

* **platforms:** add Podcast Index ([ad52b1cc](https://code.podlibre.org/podlibre/castopod/commit/ad52b1cc2b7d0bc844970214d205961a7196b4a9))