Feature/tidy up template

[cezarpopa]

Hi, i've prepared the following PR which adds the following set of changes:

1. Make all template strings translatable
2. Use short array notation
3. Fix heading elements not being in a sequentially-descending order
4. Check whether a post has a featured image set before trying to display it
5. Add the mandatory alt attribute to image tags
6. Standardise spacing/alignment across all twig views
7. Introduce a editorconfig config file.

Thank you, Cezar