added automatic release svg generation

[bhargav-j47]

this PR adds feature #2297, fixes #2297

PR introduces following changes:
Automates the generation of the release roadmap SVG using a Python script and json.
changes download page from release-roadmap.png to release-roadmap.svg

[sarahboyce]

Thank you for the PR! This is really strong

I have added some suggestions to make it easier to generate future svgs and how to make the generated image a little closer to the existing image

I think once we're happy with the generated image, we might want to consider writing a few tests

[bhargav-j47]

Hi , thank you for the review . I have added suggested changes , please do let me know if anything needs to be added

[sarahboyce]

I have suggested changes which would end up generating the following image

After commiting suggestions you will need to update the current image committed by re-running the command.
A nice to have would be if we can end the graph one line earlier and add a fade out 🤔
We still have some minor discrepancies but I think it's "close enough"

[bhargav-j47]

commited the suggested changes
-added fade at last of graph
-graph now ends one line earlier
-done changes to match the style of svg with old png

with changes release-roadmap.svg looks like this