Implement String.isSubstring and String.collate #268

	on: [push, pull_request]
	name: ci
	jobs:
	build-and-test:
	name: build-and-test
	runs-on: ubuntu-20.04 # 22.04 doesn't contain mlton
	steps:
	- uses: actions/checkout@v3
	- name: Install dependencies
	run: \|
	sudo apt-get update
	sudo apt-get install mlton lua5.3 luajit
	- name: Build
	run: make
	- name: Test (Lua)
	run: make test-lua
	- name: Test (LuaJIT)
	run: make test-luajit
	env:
	LUA_INIT_5_3: ""
	# LuaJIT: Workaround https://github.com/LuaJIT/LuaJIT/issues/859
	LUA_INIT: "local c=math.ceil;math.ceil=function(x)if-1<x and x<0 then return 0/(-1)else return c(x)end end"
	- name: Test (JS)
	run: make test-nodejs
	- name: Test (JS-CPS)
	run: make test-nodejs-cps
	- name: Test (Lua-continuations)
	run: make test-lua-continuations
	- name: Prepare third-party libraries
	run: make -C thirdparty install
	- name: Compile myself (Lua)
	run: \|
	bin/lunarml compile -o lunarml.lua --default-ann "valDescInComments error" src/lunarml.mlb
	luac -p lunarml.lua
	- name: Compile myself (LuaJIT)
	run: \|
	bin/lunarml compile --luajit -o lunarml-luajit.lua --default-ann "valDescInComments error" src/lunarml.mlb
	luajit -bl lunarml-luajit.lua > /dev/null
	- name: Compile myself and validate (JavaScript)
	run: make validate-js
	env:
	NODE_OPTIONS: "--max-old-space-size=4096"

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