feat(src): add setter methods for Calendar

Allows to change the current date of
already existing calendar.

tests(src): add tests for calendar tick functions

feat(src): implement Calendar::from_ticks for arbitrary year, add Calendar::to_ticks

So far, Calendar::from_ticks could not correctly parse
other month than the base month, this commit fixes that.

Calendar::to_ticks may convert any Calendar date to seconds passed from
the base year. The base year is remembered in Calendar instance.

chore(src): format with fmt

feat(src): split main into multiple functions

Merge pull request #1 from Rutherther/add-docs

Add basic documentation

docs: add basic documentation

Adds a readme, with images of the product,
mapping of the pins to peripherals,
the readme contains a roadmap and
description of the hardware used.

fix(src): remove unnecessary import

feat(hw): add KiCAD project, schema and pcb

chore: add MIT LICENSE

feat(tests): add full checkup testing peripherals

Tests all peripherals, observation should point
out to where an error is, if any.

feat(tests): add rtc counter test

chore: move .gitignore to root

chore(src): move source to source/ folder

feat(src): add clock application and initialization

feat(src): add brightness manager

feat(src): add module for linear interpolation

feat(src): add basic button representation

feat(src): add app state with calendar

feat(src): add CountDown abstraction