Adds Cloudflare R2 kinds tag (#27911)

## Summary & Motivation

Resolves #27882.

## How I Tested These Changes

Built UI locally and ran example snippet:

```
import dagster as dg


@dg.asset(kinds={"r2"})
def asset():
    pass


defs = dg.Definitions(assets=[asset])
```

<img width="434" alt="image"
src="https://github.com/user-attachments/assets/3b151767-475d-477f-8722-037c78fcb569"
/>


## Changelog

- [ui] adds kinds tag for Cloudflare R2

js_modules/dagster-ui/packages/ui-core/src/graph/OpTags.tsx

@@ -129,6 +129,7 @@ import python from './kindtag-images/tool-python-color.svg';
 import pytorch from './kindtag-images/tool-pytorch-color.svg';
 import pytorchlightning from './kindtag-images/tool-pytorchlightning-color.svg';
 import r from './kindtag-images/tool-r-color.svg';
+import r2 from './kindtag-images/tool-r2-color.svg';
 import rabbitmq from './kindtag-images/tool-rabbitmq-color.svg';
 import ray from './kindtag-images/tool-ray-color.svg';
 import react from './kindtag-images/tool-react-color.svg';
@@ -335,6 +336,7 @@ export type KnownTagType =
   | 'papertrail'
   | 'plural'
   | 'prefect'
+  | 'r2'
   | 'react'
   | 'reddit'
   | 'redshift'
@@ -740,6 +742,10 @@ export const KNOWN_TAGS: Record<KnownTagType, KnownTag> = {
     content: 'Ray',
     blackAndWhite: true,
   },
+  r2: {
+    icon: r2,
+    content: 'R2',
+  },
   axioma: {
     icon: axioma,
     content: 'Axioma',