Include the logos, don't generate on the fly.

docs/src/_static/README.md

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+# Iris logos
+
+[![iris-logo-title.svg](iris-logo-title.svg)](iris-logo-title.svg)
+
+Code for generating the logos is at:
+[SciTools/marketing/iris/logo/generate_logo.py](https://github.com/SciTools/marketing/blob/master/iris/logo/generate_logo.py)
+
+See the docstring of the `generate_logo()` function for more information.
+
+## Why a scripted logo?
+
+SVG logos are ideal for source-controlled projects:
+
+* Low file size, with infinitely scaling quality
+* Universally recognised vector format, editable by many software packages
+* XML-style content = human-readable diff when changes are made
+
+But Iris' logo is difficult to reproduce/edit using an SVG editor alone:
+
+* Includes correctly projected, low resolution coastlines
+* Needs precise alignment of the 'visual centre' of the iris with the centres
+  of the Earth and the image
+
+An SVG image is simply XML format, so can be easily assembled automatically
+with a script, which can also be engineered to address the above problems.
+
+Further advantages of using a script:
+
+* Parameterised text, making it easy to standardise the logo across all Iris
+  packages
+* Can generate an animated GIF/SVG of a rotating Earth