Site templates for react-admin, Clerk and Formspree

[vermakhushboo]

What does this PR do?

(Provide a description of what this PR does.)

Test Plan

(Write your test plan here. If you changed any code, please provide us with clear instructions on how you verified your changes work.)

Related PRs and Issues

(If this PR is related to any other PR or resolves any issue or related to any issue link all related PR and issues here.)

Have you read the Contributing Guidelines on issues?

(Write your answer here.)

[vermakhushboo]

Suggested change

	This is a demo of the [AppWrite](https://appwrite.io/) adapter for [react-admin](https://github.com/marmelab/react-admin).
	This is a demo of the [Appwrite](https://appwrite.io/) adapter for [react-admin](https://github.com/marmelab/react-admin).

[vermakhushboo]

@Nishantjain10 please fix if it's misspelled elsewhere as well

[vermakhushboo]

@Nishantjain10 please:

1. update env vars for all templates and mention them in the respective READMEs
2. add validation for input fields in formspree template
3. Update and review all READMEs
4. Remove banner from react-admin template
5. Take screenshots of all templates in light and dark modes
6. Clerk template has this error: [Error: > Couldn't find any pages or app directory. Please create one under the project root]

[Meldiron]

Take screenshots of all templates in light and dark modes

To take screenshot, use command docker compose exec appwrite screenshot --templateId="gallery-for-lynx" (change template ID). It will take a few minutes, and create images for you, both light and dark theme.