Update the document as Typst updates

[johanvx]

This PR contains multiple changes brought by the update of Typst.

• Use dotless.i and dotless.j for $\imath$ and $\jmath$ respectively. These symbols are available as from typst v0.4.0.
• Use datetime, which is available as from typst v0.5.0.
• Use sigma.alt for $\varsigma$. The symbol is available as from typst v0.5.0.

This PR also contains changes that improves the quality of the document.

• Remove the noidea annotation, as there's no any.
• Add the missing raw text kappa. Closes #22.
• Use compose for Ring Operator $\circ$.
• Adjust the alignment and gutters of math-code listings.

Misc.

• Add a .gitignore file.