Add support for the Allocs profiles produced by Julia's Allocs Profiler

Support for visualizing the results from the allocations profiler in
draft PR:
JuliaLang/julia#42768.

This was basically copy/pasted from
https://github.com/vilterp/AllocProfileParser.jl.

src/PProf.jl

@@ -351,6 +351,7 @@ macro pprof(ex)
 end
 
 include("flamegraphs.jl")
+include("allocs_profile.jl")
 
 
 # Precompile as much as possible, so that profiling doesn't end up measuring our own