Add documentation (#17)

* docs: update change history

* docs: compile

* docs: class option

* docs: sjtusetup

* docs: contents

* docs: use function env

* docs: theorems

* docs: refine

* docs: refine+1

* docs: add date option

* docs: add co-supervisor

* docs: update deprecated options

* docs: update subject and display-date option

* docs: update compatible interface

* docs: update \today

* docs: fix compatible cmd desc

* docs: use rEXP and EXP to distinguish cls

* docs: minor fix

* docs: no fallback for date

* docs: update style options

* docs: update draft option

* docs: add use cases

* docs: update titlepage option

* docs: update type

* docs: \frontmatter thesis only

* docs: update requirements

* docs: update header-font default

* docs: remove v1 changes

* docs: update font

* docs: update credits

* docs: update degree

* docs: \fixedlineskip and float-font default

* docs: update float-font default

* docs: update title info

* docs: update

Co-authored-by: Alexara Wu <[email protected]>