docs: fix retired JSON escape link

[coderaviverma]

Proposed change

The page-template guide sends readers to a retired JSON Escape page when explaining how to insert minified HTML into a JSON form definition. This replaces that unavailable destination with the live JSON Escape tool, fixes the nearby “pasting the” typo, and states that the tool returns escaped content without surrounding quotes.

I am affiliated with JSONViewerTool, the replacement site. The change is limited to the broken destination and the output-format clarification.

Jira ticket: N/A — external documentation correction

Type of change

• Bug fix
• New feature
• Breaking change
• Misc. (documentation, build updates, etc)

Checklist

• You have executed this code locally and it performs as expected.
• You have added tests to verify your code works. (No new tests are required for this one-line documentation correction; the production Docusaurus build passed.)
• You have added code comments and JSDoc, where appropriate. (Not applicable.)
• There is no commented-out code.
• You have added developer docs in README.md and docs/* (where appropriate, e.g. new features). (This change is itself in docs/*.)
• The tests are passing (npm run test). (Not run locally because no application code changed; repository CI will run the full unit-test matrix.)
• The linting checks are passing (npm run lint). (Only the edited Markdown file was checked locally; repository CI will run the full lint matrix.)
• The code has been formatted (npm run format).

Validation performed:

• git diff --check
• npx --no-install prettier --check docs/features/configuration-based/page-templates.md
• npm run docs:build (passed; existing unrelated documentation-link and Sass deprecation warnings remain)