Update get_started section in README

[Mr-Geekman]

IMPORTANT: Please do not create a Pull Request without creating an issue first.

Before submitting (must do checklist)

• Did you read the contribution guide?
• Did you update the docs? We use Numpy format for all the methods and classes.
• Did you write any new necessary tests?
• Did you update the CHANGELOG?

Type of Change

• Examples / docs / tutorials / contributors update
• Bug fix (non-breaking change which fixes an issue)
• Improvement (non-breaking change which improves an existing feature)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Proposed Changes

Look #491.

Related Issue

#491.

Closing issues

Closes #491.

[codecov-commenter]

Codecov Report

Merging #569 (fd4ae29) into master (a8fcfa3) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #569   +/-   ##
=======================================
  Coverage   86.80%   86.80%           
=======================================
  Files         119      119           
  Lines        5739     5739           
=======================================
  Hits         4982     4982           
  Misses        757      757           

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[iKintosh]

Suggested change

	from etna.transforms import DateFlagsTransform
	from etna.transforms import DensityOutliersTransform
	from etna.transforms import FourierTransform
	from etna.transforms import LagTransform
	from etna.transforms import LinearTrendTransform
	from etna.transforms import SegmentEncoderTransform
	from etna.transforms import TimeSeriesImputerTransform
	from etna.transforms import DateFlagsTransform, DensityOutliersTransform, FourierTransform, LagTransform, \
	LinearTrendTransform, SegmentEncoderTransform, TimeSeriesImputerTransform

[iKintosh]

Suggested change

	DateFlagsTransform(
	day_number_in_week=True,
	day_number_in_month=True,
	is_weekend=True,
	week_number_in_month=True,
	out_column="date_flag",
	),
	DateFlagsTransform(is_weekend=True, week_number_in_month=True, out_column="date_flag"),

[iKintosh]

👍