Fix loading ER diagram format from .tbls.yml

[k1LoW]

Fix #119

[codecov]

Codecov Report

Merging #120 into master will decrease coverage by 0.02%.
The diff coverage is 0%.

@@            Coverage Diff             @@
##           master     #120      +/-   ##
==========================================
- Coverage   72.61%   72.58%   -0.03%     
==========================================
  Files          12       12              
  Lines        2509     2510       +1     
==========================================
  Hits         1822     1822              
- Misses        521      522       +1     
  Partials      166      166

Impacted Files	Coverage Δ
config/config.go	46.45% <0%> (-0.19%)	⬇️

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