Include on-device training release blog.
### Description
<!-- Describe your changes. -->
Included entry for on-device training release blog.
### Motivation and Context
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- If it fixes an open issue, please link to the issue here. -->
Provides latest updates in the blog.
### Description
Move Vitis AI EP from community maintained to main EP list
### Motivation and Context
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### Description
This PR is to simplify our blog updating process in order to make sure
it stays up to date. I have added a tempalte and a json source where
blogs can be easily added. I have removed the images from the blogs, and
deleted the old images. Additionally we decided to remove twitter from
the header.
https://cassiebreviu.github.io/onnxruntime/blogs.html
### Motivation and Context
<!-- - Why is this change required? What problem does it solve?
- If it fixes an open issue, please link to the issue here. -->
