Document Fastmail's new EU data region option

Fastmail now offers an EU data region (Amsterdam), in addition to its
existing US infrastructure, so it's no longer accurate to say Fastmail
only hosts data in the US. Update the advantages/disadvantages
accordingly and note that EU-based users no longer need to pick an
alternative provider purely for EU hosting reasons.

Also ignore the local .venv/ directory, used to install docutils so
Vale's lintRST rule can shell out to rst2html.

Assisted-by: LLM [research, plan, codegen]
Signed-off-by: Konstantin Ryabitsev <konstantin@linuxfoundation.org>