Adiciona desafio 15 ao site #684

	name: Presubmit tests
	on: [pull_request]
	jobs:
	pr_tests:
	runs-on: ubuntu-latest
	steps:
	- name: Install Go
	uses: actions/setup-go@v2
	with:
	go-version: 1.15.x

	- name: Checkout code
	uses: actions/checkout@v2
	with:
	persist-credentials: false
	submodules: true # Fetch Hugo themes.

	- name: Check files with invalid UTF-8 content
	run: \|
	./ci/utfcheck.sh

	- name: Setup Hugo
	uses: peaceiris/actions-hugo@v2
	with:
	hugo-version: '0.139.2'

	- name: Build Site
	run: hugo

	- name: Build checkparticipantes
	run: \|
	pushd ci && go build -o checkparticipantes && popd

	- name: Validates PARTICIPANTES.md
	run: ci/checkparticipantes PARTICIPANTES.md

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