docs: add note about tracking todo items with todui to readme

docs: track features with a todo list in repo

docs: add mention of pre-built Windows binary

build: add windows back into cross compilation array

tasks: remove workaround for resetting terminal state

deps: update libvaxis

docs: add installation instructions to readme

cli: update todui version on main branch and in changelog

build: add build option to cross compile for macos and linux

docs: fix usage help text

docs: add a contributing file

docs: add a note on feature-completeness to the readme

docs: update screenshots

tasks: fix completed task list height calculation

tasks: ensure selected task is visible after change