Added main to DOM components

[carmas123]

Description

Changed the generatehtml.dart to be able to pass a custom tag value from json definition file, in order to be able to create a "main" html tag usgin a custom function "main" without have conflicts with the main() Dart method.

Type of Change

✨ New feature or improvement

Ready Checklist

• [X] I've read the Contribution Guide.
• [X] In case this PR changes one of the core packages, I've modified the respective CHANGELOG.md file using the semantic_changelog format.
• [X] I updated/added relevant documentation (doc comments with ///).
• [ ] I added myself to the AUTHORS file (optional, if you want to).

[github-actions[bot]]

Package Version Report

The following packages have been updated: jaspr : 0.11.1 -> 0.11.2 jaspr_builder : 0.11.1 -> 0.11.2 jaspr_cli : 0.11.1 -> 0.11.2 jaspr_router : 0.4.0 -> 0.4.1 jaspr_test : 0.11.1 -> 0.11.2