Make setting_warning annotation optional

See https://github.com/edx/code-annotations/blob/master/CHANGELOG.rst#102---2021-01-22

Fix annotation grouping

See: https://github.com/edx/code-annotations/blob/master/CHANGELOG.rst#101---2021-01-22

Implement optional fields

See: https://github.com/edx/code-annotations/blob/master/CHANGELOG.rst#100---2021-01-25

Improve logging when we fail to process a file because

See: https://github.com/edx/code-annotations/blob/master/CHANGELOG.rst#0102---2020-11-09

Fix Github links generated by the sphinx extension for settings

See: https://github.com/edx/code-annotations/blob/master/CHANGELOG.rst#0101---2020-11-09

Fix table of contents generated by sphinx extensions

See https://github.com/edx/code-annotations/blob/master/CHANGELOG.rst#0100---2020-10-12

Removed unused 'documented_elsewhere' annotation

See https://github.com/edx/code-annotations/blob/master/CHANGELOG.rst#090---2020-09-25

Settings annotations and Sphinx extension

See https://github.com/edx/code-annotations/blob/master/CHANGELOG.rst#080---2020-09-10

Simplify feature toggle annotations

See https://github.com/edx/code-annotations/blob/master/CHANGELOG.rst#070---2020-09-07

Multi-line annotation improvement

See https://github.com/edx/code-annotations/blob/master/CHANGELOG.rst#060---2020-08-27