ansicolor_sink.h - add missing sink include

Change the default value for SPDLOG_BUILD_xxx

The value based on whether spdlog is used as a third-party dependency or
as a standalone project. If spdlog is included through add_subdirectory,
the tests/examples/benchmarsk are disabled by default, and if spdlog is
configured standalone, then they are enabled by default.

Revert "Add `conda` to package managers in README"

Add `conda` to package managers in README

Add set_sinks method to dist_sink