Version 6 Release

[dan-fritchman]

Primary goal(s):

• Roll in #157

Also shall include:

• https://github.com/Vlsir/Vlsir/pull/89

• 218 (by whatever means work as of release time)

• Similar treatment for other PDK packages
• Everything else already merged to main

Nice to have (i.e. if they're merged they're in, if not they're not):

• 49 / #219

Not to be included:

• 215

• 216

• 217

• Any other open issues

[dan-fritchman]

Published at https://pypi.org/project/hdl21/6.0.0/.
Commentary for v7 welcome on #225.