Replacement of dead links (#423)

* Update repository link on Cargo.toml

* Update repository for Cargo.toml [WASM]

* Update link on CONTRIBUTING.md

Moving <https://github.com/jasonwilliams/boa/issues> to <https://github.com/boa-dev/boa/issues>

* Remove dead links on CHANGELOG.md

Changes all dead links from <https://github.com/jasonwilliams/boa> to <https://github.com/boa-dev/boa>.

* Fix dead link on boa/Cargo.toml

From <https://github.com/jasonwilliams/boa> to <https://github.com/boa-dev/boa>

* CHANGELOG.md - Fix link on comparing v0.7.0 with v0.8.0

Previously comparing v0.7.0...HEAD