Add a button to the "Beam Bridge documentation section" hosted on the beam.mw website to move through pages.

[ddanairaza]

1. Add a button on this page for next page "beam.mw/docs/bridges" to "https://beam.mw/docs/bridges/creating-cross-chain-transactions"

2. Add a button on this page for next page to "https://beam.mw/docs/bridges/creating-cross-chain-transactions" to "https://beam.mw/docs/bridges/joining-the-beam-community-and-next-steps"