fix/front matter template

[sywhb]

• fix: download content and file attachment only if included in the template
• fix: allow adding aliases to the variables in the front matter
• feat: add more variables in the front matter setting
• feat: add a optional front matter template under advanced settings
• feat: add link to our discord server in the settings

[jacksonh]

Doing some local testing

[github-actions[bot]]

:tada: This PR is included in version 1.4.0 :tada:

The release is available on GitHub release

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