docs: Fix warning and treat them as errors (#666)
docs: Fix warning and treat them as errors (#666)

The CI is not able to catch many documentation problems because we are ignoring
warnings. This commit fixes most of the warnings, ignores the rest and enables
a flag to treat them as errors.

Co-authored-by: Diego Hurtado <2bc8d855c0e6dd74eb47b0b9f8b97160279b08b1@users.noreply.github.com>
open-telemetry/opentelemetry-python-contrib,open-telemetry/opentelemetry-python-contrib,open-telemetry/opentelemetry-python-contrib