add README.md

README.md

+1. Rename .env.example to .env and set your settings
+2. Rename alembic.ini.example to alembic.ini and set sqlalchemy.url field
+3. Install dependencies from requirments.txt file
+4. Create tables for database using sql\create-dump.sql or apply migration using the command "alembic upgrade head" in src directory
+5. In src directory use "scrapy crawl books" command for start parsing.
\ No newline at end of file