Distinguish between inline equations and block equations

[OrangeX4]

Currently, Lexer treats a single dollar sign and multiple dollar signs as the same token, so we can't distinguish between an inline equation and a block equation.

mitex/crates/mitex-lexer/src/lib.rs

Lines 433 to 434 in 41a666c

	#[regex(r"\$\$?")]
	Dollar,

[Myriad-Dreamin]

This can be distinguished by checking the content of the dollar token