Please add SPDX lines in license headers.

[SanthiSridharan]

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Include the following lines in the license headers within the scripts. This is to ensure that the automated license scanning tools can identify the license.

SPDX-Copyright: Copyright (c) Capital One Services, LLC
SPDX-License-Identifier: Apache-2.0

[marzolfb]

As mentioned in #68, I added a script to automate fixing up the license headers. Here's the output I got when I ran the script:

./check-license-headers.sh
Beginning license header check ...
Adding license header for ../src/__mocks__/react-native-svg.js...
Adding license header for ../src/__tests__/pie/PieBasic-test.js...
Adding license header for ../src/__tests__/scatterplot/ScatterplotBasic-test.js...
Adding license header for ../src/__tests__/SmoothLine/SmoothLineBasic-test.js...
Adding license header for ../src/__tests__/SmoothLine/SmoothLineRegions-test.js...
Adding license header for ../src/__tests__/SmoothLine/SmoothLineRegionsExtended-test.js...
Adding license header for ../src/__tests__/stockline/StockLineBasic-test.js...
Adding license header for ../src/__tests__/stockline/StockLineDynamicTickLabels-test.js...
Adding license header for ../src/__tests__/stockline/StockLineStaticTickLabels-test.js...
Adding SPDX lines in license header for ../src/Axis.js...
Adding SPDX lines in license header for ../src/Bar.js...
Adding SPDX lines in license header for ../src/index.js...
Adding SPDX lines in license header for ../src/Line.js...
Adding SPDX lines in license header for ../src/Pie.js...
Adding SPDX lines in license header for ../src/Radar.js...
Adding SPDX lines in license header for ../src/Scatterplot.js...
Adding SPDX lines in license header for ../src/SmoothLine.js...
Adding SPDX lines in license header for ../src/StockLine.js...
Adding SPDX lines in license header for ../src/Tree.js...
Adding SPDX lines in license header for ../src/util.js...
Adding SPDX lines in license header for ../example/src/App.js...
Adding SPDX lines in license header for ../example/src/bar/BarChartColumnBasic.js...
Adding SPDX lines in license header for ../example/src/Home.js...
Adding SPDX lines in license header for ../example/src/Menu.js...
Adding SPDX lines in license header for ../example/src/pie/PieChartBasic.js...
Adding SPDX lines in license header for ../example/src/radar/RadarChartBasic.js...
Adding SPDX lines in license header for ../example/src/scatterplot/ScatterplotChartBasic.js...
Adding SPDX lines in license header for ../example/src/smoothline/SmoothLineChartBasic.js...
Adding SPDX lines in license header for ../example/src/smoothline/SmoothLineChartRegions.js...
Adding SPDX lines in license header for ../example/src/smoothline/SmoothLineChartRegionsExtended.js...
Adding SPDX lines in license header for ../example/src/stockline/StockLineChartBasic.js...
Adding SPDX lines in license header for ../example/src/stockline/StockLineChartDynamicTickLabels.js...
Adding SPDX lines in license header for ../example/src/stockline/StockLineChartStaticTickLabels.js...
Adding SPDX lines in license header for ../example/src/tree/TreeChartBasic.js...
Done!