[#2169] Improve mail-template styling

[jiromaykin]

detailed issue: https://taiga.maykinmedia.nl/project/open-inwoner/task/2169

overall issue: https://taiga.maykinmedia.nl/project/open-inwoner/task/2134

These mostly concern case_document_notification , case_status_notification_action_required and case_status_notification.

ToDo

• - add a little bit more placeholder-data so CKeditor preview/Testmails look nicer
• - Spacing between 'met vriendelijke groet…' and 'dit bericht is automatisch…' 2X
• - faulty whitespace in white rounded-border area
• - add sharper/higher rez icons
• - check if there is extra whitespace in the empty columns (making the wrapping Table responsive, max width 600px)
• - correct the blue info hex color
• - Spacing 'login' + "U hoeft niets te doen" needs to be larger (info notificatie)  
• - "Log in" should not be underlined (info notificatie)
• - Cell-widths tablecells for phonenumber and contactlink should be reversed (2X)

EXTRA

• align-right for 1 right-column + align left on mobile
• small CKEditor style improvements

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 95.00%. Comparing base (c677c1d) to head (b9f4322).

❗ Current head b9f4322 differs from pull request most recent head 3e80445. Consider uploading reports for the commit 3e80445 to get more accurate results

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #1072   +/-   ##
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  Coverage    95.00%   95.00%           
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  Files          894      894           
  Lines        31404    31405    +1     
========================================
+ Hits         29834    29835    +1     
  Misses        1570     1570           

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[pi-sigma]

Template language should be consistent

[pi-sigma]

Should the text be Dutch?

[jiromaykin]

Probably, but this PR for #2169 is really only about styling and about the 3 case_status templates; I'd rather change all the 'other templates properly in task #2120 - I just wanted to do a small correction for the paragraphs here.

[alextreme]

Mag gemerged worden na verhelpen conflict