Add Project.toml

[ron-wolf]

Make it possible to install the package using Pkg3, whereas currently the package manager unexpectedly adds an incompatible package by @jwscook, causing confusion and frustration.

Adding the package that ContinuedFractions resolves to by default

(@v1.4) pkg> add ContinuedFractions#master
    Cloning git-repo `https://github.com/jwscook/ContinuedFractions.jl.git`
   Updating git-repo `https://github.com/jwscook/ContinuedFractions.jl.git`
  Resolving package versions...
   Updating `~/.julia/environments/v1.4/Project.toml`
  [11738ef7] + ContinuedFractions v0.1.0 #master (https://github.com/jwscook/ContinuedFractions.jl.git)
   Updating `~/.julia/environments/v1.4/Manifest.toml`
  [11738ef7] + ContinuedFractions v0.1.0 #master (https://github.com/jwscook/ContinuedFractions.jl.git)

Trying to add this repo manually

(@v1.4) pkg> add https://github.com/johnmyleswhite/ContinuedFractions.jl
    Cloning git-repo `https://github.com/johnmyleswhite/ContinuedFractions.jl`
   Updating git-repo `https://github.com/johnmyleswhite/ContinuedFractions.jl`
ERROR: could not find project file in package at https://github.com/johnmyleswhite/ContinuedFractions.jl