v0.6.0

This release includes the following features:

• fetch_dev_utils_manual action: Download eProsima dev-utils (#38).
• fetch_ddspipe_manual action: Download eProsima ddspipe (#39).
• fetch_fastdds_manual action: Download eProsima Fast DDS (#35).
• New external action: download artifact (#38).

This release also fixes the empy package version to avoid conflicts when installing colcon core (#42).

PRs in merge order:
#35, #38, #39, #40, #41, #42