Add a LaTeX formatting style file

[namasikanam]

Add a LaTeX formatting style file for EasyCrypt, which is on top of listings. Note the existence in readme.

[strub]

@namasikanam Are the keyword lists up to date? (You can use scripts/srctx/keywords < src/ecLexer.mll to extract the list)

[MM45]

Also, since this is now a sty file, I think the \makeatletter and \makeatother can be removed?

[namasikanam]

@namasikanam Are the keyword lists up to date? (You can use scripts/srctx/keywords < src/ecLexer.mll to extract the list)

@strub Updated to the latest keywords list now. BTW, for and match appear twice in the lexer.

Also, since this is now a sty file, I think the \makeatletter and \makeatother can be removed?

@MM45 I was not aware that these are unnecessary in .sty file. They're removed.