[pytx] Add dev environment setup guidelines to CONTRIBUTING.md (#1296) #1016

	# Copyright (c) Meta Platforms, Inc. and affiliates.

	name: python-threatexchange CI
	on:
	push:
	branches:
	- main
	paths:
	- "python-threatexchange/**"
	- ".github/workflows/python-threatexchange-ci.yaml"
	pull_request:
	branches:
	- main
	paths:
	- "python-threatexchange/**"
	- ".github/workflows/python-threatexchange-ci.yaml"

	defaults:
	run:
	working-directory: python-threatexchange

	jobs:
	lint-and-types:
	name: Lint and Type-Check python
	runs-on: ubuntu-latest
	steps:
	- uses: actions/checkout@v2
	- uses: actions/setup-python@v2
	with:
	python-version: "3.11"
	- name: Install dependencies
	run: \|
	python -m pip install --upgrade pip
	python3 -m pip install -e .[all]
	- name: Check code format
	run: \|
	black --check .
	- name: Check python types
	run: \|
	python -m mypy threatexchange
	test:
	runs-on: ubuntu-latest
	strategy:
	matrix:
	python-version: ['3.8', '3.9', '3.x']
	steps:
	- uses: actions/checkout@v2
	- name: Setup Python ${{ matrix.python-version }}
	uses: actions/setup-python@v2
	with:
	python-version: ${{ matrix.python-version }}
	- name: Install ffmpeg
	id: ffmpeg
	run: \|
	sudo apt-get update
	sudo apt-get install ffmpeg
	- name: Install dependencies
	run: \|
	python -m pip install --upgrade pip
	pip install -e ".[test]"
	- name: Test with pytest
	run: \|
	py.test

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