Add more references

[freedomofkeima]

If you know any awesome places, events, and resources related to otaku subculture in Japan, feel free to open a pull request and append the list!

For places, if it is possible, try to avoid series-specific pilgrimage since it might clutter the list.

For events, I'm expecting that the event should have more than 10,000 attendees.

Thank you 😄

[goelrohan6]

@freedomofkeima #2