added workflow_dispatch #16

	# name of the workflow: will be displayed in the Actions tab of the repository
	name: Hello world workflow
	# on: specifies the events that trigger the workflow
	on:
	# event 1: on each push
	push:
	# filter: only trigger when pushed to main branch
	branches:
	- main
	# event 2: on each pull request
	pull_request:
	# filter: only trigger when PR is opened or synchronized to main branch
	branches:
	- main
	# event 3: on manual trigger: displayed in the Actions tab of the repository
	workflow_dispatch:

	# jobs: a list of jobs that run in parallel
	jobs:
	# job 1 name: hello_job
	hello_job:
	# runs-on: specifies the runner for the job
	runs-on: ubuntu-latest
	# steps: a list of steps that run in sequence. each step is separated by '-'
	steps:
	# step 1 name: checkout: uses the actions/checkout action to checkout the repository
	- uses: actions/checkout@v2 # add prebuilt action here when needed in user/repo@[version\|commit\|branch] format
	name: Checkout repository
	# step 2 name: Hello world step: prints "Hello world"
	- name: Hello world step # name of the step [optional]
	run: echo "Hello world" # run command directly
	shell: bash

	# job 2 name: goodbye_job
	goodbye_job:
	# runs-on: specifies the runner for the job
	runs-on: ubuntu-latest
	# steps: a list of steps that run in sequence. each step is separated by '-'
	steps:
	# step 1 name: Goodbye world step: prints "Goodbye world"
	- name: Goodbye world step # name of the step [optional]
	run: echo "Goodbye world" # run command directly
	shell: bash

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