Add effect annotations

[devmotion]

Fixes #37.
Fixes #40.

With this PR I get:

julia> using IrrationalConstants, BenchmarkTools

julia> @btime 3.0 ≤ pi
  1.041 ns (0 allocations: 0 bytes)
true

julia> @btime 3.0 ≤ invsqrt2
  1.083 ns (0 allocations: 0 bytes)
false

Note: To keep up with recent changes in Base, additionally #36 is needed which fixes CI.

[coveralls]

Pull Request Test Coverage Report for Build 13032954318

Details

• 6 of 6 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 100.0%

---

Totals
Change from base Build 13032809262:	0.0%
Covered Lines:	70
Relevant Lines:	70

---

💛 - Coveralls

[stevengj]

Great, thanks! Can we tag a new release? You are way ahead of me: JuliaRegistries/General#123932