Powerpoint/Google Slides file generation (#471)

* generate ppt

Signed-off-by: David Longworth <djl@sent.com>

* add powerpoint generator script

Signed-off-by: David Longworth <djl@sent.com>

* add missing icons

Signed-off-by: David Longworth <djl@sent.com>

* lint

Signed-off-by: David Longworth <djl@sent.com>

* typescript nonsence

Signed-off-by: David Longworth <djl@sent.com>

* more icons

Signed-off-by: David Longworth <djl@sent.com>

* docs

Signed-off-by: David Longworth <djl@sent.com>

* ignore error

custGeom isn’t listed as a type gitbrent/PptxGenJS#1328

Signed-off-by: David Longworth <djl@sent.com>

* move to preview folder

Signed-off-by: David Longworth <djl@sent.com>

---------

Signed-off-by: David Longworth <djl@sent.com>

Author: abovedave

README.md

@@ -234,6 +234,17 @@ Take these hash values and use them as the values for the previously added entri
 
 When updating an existing icon, just update the corresponding hash value(s) for the property combination(s) that changed.
 
+### Syncing to Google Slides/PowerPoint
+
+Optionally, you can generate a `.pptx` file which will contain the `Size=64` and `Spot/*` assets as native vectors, allowing you to recolor and scale. We maintain a [publicly available version of this](https://docs.google.com/presentation/d/1sisvc-ZBWxUsas10wlMGaT5MZX4nw85lIyReGPz5pqc/edit) for internal and external folks.
+
+```
+npm run build
+
+# Not part of the main build process (yet)
+npm run generate:powerpoint
+```
+
 ## Publishing a new release
 
 In order to publish a new release to npm and NuGet, you just need to tag a new release and push it to origin: