Exclude markdownlint from CI

[pre-commit.ci] pre-commit autoupdate

Bump actions/checkout from 5 to 6

Re-license project as LGPLv3

Release 1.0.3

doc: Make RTD build reproducible

lint: Remove unused pycodestyle rules

devcontainer: Fix build

exporter: Fix mypy issues

devcontainer: Update definition

ci: Upgrade actions

pymarkdown: Update deprecated functions

ci: Ignore zipp dependency security issue

python: Replace peakrdl with peakrdl-cli dependency

python: Deprecate 3.6 and upgrade dev env to 3.12