feat: create theme

Create theme with graphic charter

• Logo
• Colors
• Fonts

source nextcloud: Lydra/10 - Communication/00 - Identité graphique/2018.07.24 lydra identite graphique version finale/charte_lydra_A4.pdf

added To Do label

assigned to @Plumtree3D

changed the description

added Doing label and removed To Do label

created branch 2-feat-create-theme to address this issue

mentioned in merge request !2 (merged)

marked the checklist item Logo as completed

marked the checklist item Colors as completed

marked the checklist item Fonts as completed

added Need review label and removed Doing label

mentioned in commit 884c2ca0

closed with merge request !2 (merged)