consolidate usage of placeholder text

[josefaidt]

Is your feature request related to a problem? Please describe.

examples:

• backend/api/~apiname~/schema.graphql
• amplify/backend/api/YOUR-API-NAME/build (on the same page, italicized and not inline code block)
• AUTH_<RESOURCE_NAME>_USERPOOLID
• amplify:<resource_name>
• https://<API ID 1>.execute-api.eu-west-2.amazonaws.com/dev/items
• https://{restapi-id}.execute-api.{region}.amazonaws.com/{environment}/{path}. (same page)

This is not an example of placeholder text that will need to be consolidated:

Here is an example of the proposed, standardized placeholder text

amplify/backend/auth/<resource-name>/

Describe the solution you'd like

using an inline code block, refer to placeholder text with angle brackets, lowercase, kebab-case. When referring to files in the amplify directory, always preface with amplify/

refer to your schema at `amplify/backend/api/<api-name>/schema.graphql`

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.

Additional context
Add any other context or screenshots about the feature request here.