Add MSSQL to supported database list of intall page

[sapk]

Fix (partially ?) #3357

[lunny]

LGTM

[codecov-io]

Codecov Report

Merging #3359 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #3359   +/-   ##
=======================================
  Coverage   35.05%   35.05%           
=======================================
  Files         280      280           
  Lines       40565    40565           
=======================================
  Hits        14219    14219           
- Misses      24242    24243    +1     
+ Partials     2104     2103    -1

Impacted Files	Coverage Δ
modules/process/manager.go	76.81% <0%> (-4.35%)	⬇️
models/repo_list.go	65.62% <0%> (-1.57%)	⬇️
models/repo.go	43.37% <0%> (+0.18%)	⬆️
models/repo_indexer.go	53.88% <0%> (+0.97%)	⬆️

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