[RFC007] Add a builder module for the new AST #304

	# This is the part of the benchmark runner that runs on pull requests.
	# It's separate from the master runner for two reasons:
	# - to track it differently on bencher.dev, because we only want to use master as
	# the historical baseline for comparison
	# - because it might want to run on PRs from forks, and those don't get access to the
	# bencher API key.
	#
	# See the [bencher docs] for more details.
	#
	# [bencher docs]: https://bencher.dev/docs/how-to/github-actions/#benchmark-fork-pr-and-upload-from-default-branch

	name: benchmark pull requests
	on:
	pull_request:
	types: [opened, reopened, edited, synchronize]

	jobs:
	benchmark-pr:
	name: benchmark pr
	runs-on: ubuntu-latest
	steps:
	- uses: actions/checkout@v4
	with:
	fetch-depth: 0
	- uses: cachix/install-nix-action@v30
	name: "Installing Nix"
	with:
	extra_nix_config: \|
	experimental-features = nix-command flakes
	accept-flake-config = true
	nix_path: "nixpkgs=channel:nixos-unstable"
	- name: run benchmarks
	run: \|
	nix develop --command cargo bench --package nickel-lang-core --features=benchmark-ci --bench numeric --bench arrays > criterion-output.txt
	- name: upload results
	uses: actions/upload-artifact@v4
	with:
	name: criterion-output
	path: criterion-output.txt
	- name: Upload GitHub Pull Request Event
	uses: actions/upload-artifact@v4
	with:
	name: event.json
	path: ${{ github.event_path }}

Provide feedback