Incompatibility with mkdocs 1.2.

Describe the bug The new released mkdocs 1.2 includes livereload, not as a dependency. Resulting in an import error:

  File "/usr/local/lib/python3.9/site-packages/mkdocstrings/plugin.py", line 18, in <module>
    from livereload import Server
ModuleNotFoundError: No module named 'livereload'

To Reproduce Steps to reproduce the behavior:

1. pip install mkdocstrings
2. python -c 'import mkdocstrings.plugin'

Expected behavior No error.

Information (please complete the following information):

• mkdocstrings version: 0.15.1

[oprypin]

The release with the fix is now out.

@themightychris @jaceklaskowski @plannigan @deepcharles @lyz-code @Midnighter @coady @yi2020 (notifying users who linked workarounds from commits elsewhere)

[oprypin]

Sorry, looks like for now a workaround will have to be used, until a new release with the fix can be made.

• For now, manually add ‘livereload’ to your list of library requirements
• Or, pin MkDocs to an older version