we need more limit solvers

[MomoDeve]

here are some missing cases:

• [x] lim(x -> inf) (1 + 1/x)^x
• [x] lim(x-> 0) sin(x) / x
• [ ] lim(x -> inf) e^x - x more cases will be added here

[WhiteBlackGoose]

@MomoDeve 2 out of 3 are closed. But it seemingly does not recognize functions of higher order.