[WIP] Add migration guide for 2.0

src/docs/migrate2.md

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+# Migrate to Semiotic 2.0
+
+**What's New in 2.0** This document outlines the high-level differences between 1.x and 2.0 releases.
+For detailed information about changes, see Semiotic's [Change Log](CHANGELOG.md).
+
+## Installing 2.0
+
+TODO: Add installation and a usage example; highlight any non-obvious steps
+
+## Major Changes
+
+- React 17 Compatibility
+    - Remove deprecated lifecycle events
+    - Transition most components to functional components using hooks
+- RoughJS is now optional
+    - You need to import RoughJS (or anything that follows its pattern)
+    - send it as the `sketchyRenderingEngine` prop of a frame for it to honor the `renderMode` options that were honored automatically in 1.0
+- Dramatically Improved Build and Tooling
+    - Smaller package sizes
+    - Faster builds using Parcel
+- `Areas` in `XYFrame` are now `Summaries`
+    - Renamed components and files to `Summaries`
+    - For example, `canvasAreas` has been renamed to `canvasSummaries`
+- Removed download data functionality
+
+## Improvements
+
+### Canvas
+- Canvas progressive rendering is improved
+- Progressive rendering can be disabled via the `disableProgressiveRendering`
+  prop on a frame
+
+### Frames
+- `frameRenderOrder` allows you to change the render order of elements in frames
+ (you can even render them twice if you want them to sandwich another layer
+of elements) takes an array of any or all (with duplicates) of these values:
+ `["axes-tick-lines", "viz-layer", "matte", "axes-labels", "labels"]` which you can rearrange.
+- `filterRenderedNodes`, `filterRenderedLines`, `filterRenderedPoints`, `filterRenderedSummaries` props on NetworkFrame and XYFrame that take a filter function and will apply the filter on the drawn viz after it's been created (useful for filtering Partition layouts and things like that)
+- `lineBounds` summaryType in XYFrame (to create bounding regions around a line) takes `boundingAccessor` (when bounds above and below are the same), `topBoundingAccessor` and `bottomBoundingAccessor` to let you draw asymmetric bounding regions around a line.
+
+### Charts
+
+#### Boxplot chart
+
+- 1.5IQR Outliers for Boxplot via `outliers: true` on the summaryType that
+  pulls all points outside of 1.5 IQR and draws them as individual points
+  outside the whiskers.
+
+#### Trendline chart
+
+- Trendline can now show the formula as a decoration via `showSlope: true` 
+  in the summary object
+
+#### Violin chart
+
+- Multipart Violin via `subsets: fn => { returns filterAppliedOnViolinData }`
+  on the `summaryType` allows you to draw more than one violin plot overlapping
+  on the same column
+- Add IQR viz to violin via `iqr: true` in the type object
+
+### Actions and events
+
+- Clickable Legend Events
+- Pass raw event to interaction events