Add h1 title to documentation pages

[faustinoaq]

Hi @imdrasil jennifer looks amazing!

We are using Jennifer at Amber too

This issue is a suggestion to add h1 title to he following pages:

• https://amberframework.org/guides#/imdrasil/jennifer.cr/master/docs/configuration.md
• https://amberframework.org/guides#/imdrasil/jennifer.cr/master/docs/migration.md
• https://amberframework.org/guides#/imdrasil/jennifer.cr/master/docs/model_mapping.md
• https://amberframework.org/guides#/imdrasil/jennifer.cr/master/docs/model_sti.md
• https://amberframework.org/guides#/imdrasil/jennifer.cr/master/docs/callbacks.md
• https://amberframework.org/guides#/imdrasil/jennifer.cr/master/docs/validation.md
• https://amberframework.org/guides#/imdrasil/jennifer.cr/master/docs/timestamps.md
• https://amberframework.org/guides#/imdrasil/jennifer.cr/master/docs/relations.md
• https://amberframework.org/guides#/imdrasil/jennifer.cr/master/docs/crud.md
• https://amberframework.org/guides#/imdrasil/jennifer.cr/master/docs/query_dsl.md
• https://amberframework.org/guides#/imdrasil/jennifer.cr/master/docs/eager_loading.md
• https://amberframework.org/guides#/imdrasil/jennifer.cr/master/docs/pagination_and_ordering.md
• https://amberframework.org/guides#/imdrasil/jennifer.cr/master/docs/model_scopes.md
• https://amberframework.org/guides#/imdrasil/jennifer.cr/master/docs/aggregation.md
• https://amberframework.org/guides#/imdrasil/jennifer.cr/master/docs/transaction_and_lock.md

I wrongly added a copyright message to bottom page, maybe I can delete this message or replace it with a new one 😅

Thanks you for jennifer!

[imdrasil]

@faustinoaq done. About "copyright" - actually this lib is under the MIT license so I can ask you to switch only to "copyleft" but I'm not sure for proper format ) will think about it and ping you

[faustinoaq]

@eliasjpr @elorest @drujensen WDYT about copyright message on amber guides footer ?

Maybe can we use some Creative Common License for documentation ?