Add prefaces to main sections in DG

[lamlaaaam]

Resolves #168

[codecov]

Codecov Report

Merging #194 into master will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             master     #194   +/-   ##
=========================================
  Coverage     72.54%   72.54%           
  Complexity      516      516           
=========================================
  Files            83       83           
  Lines          1548     1548           
  Branches        154      154           
=========================================
  Hits           1123     1123           
  Misses          370      370           
  Partials         55       55           

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update bb01806...bb2bb4c. Read the comment docs.