Create an action to run benchmarks in a PR

[suvayu]

Create an action similar to what Tulipa does, which can be triggered in a PR as required.

[datejada]

I realized that you need to add the SpineJuliaRegistry to install version from there, otherwise it fails since SpineOpt and SpineInterface are not in the JuliaRegistry:

using Pkg									# Use the package manager. Alternatively, use `]` in REPL
pkg"registry add General https://github.com/spine-tools/SpineJuliaRegistry"	# Add SpineJuliaRegistry as an available registry for your Julia