add erlang-pure-migrations to curated list

[bearmug]

Dear awesome list curators, here is one more tool, which I propose for the list adoption.

What Awesome onboarding for database version control engine erlang-pure-migrations.

Why

• PostgreSQL/MySQL support out-of-the-box
• a number of real and continuously verified integrations (3 for PostgreSQL and 1 for MySQL)
• reasonable errors and problems reporting
• built-in quality controls metrics
• extensive usage code snippets for each integration
• effects-free engine with detailed mechanics explanation