docs: What's new in v5.1 

* master:
  build: only lint the pkg folder
  changelog: adds note about closing #11476
  singlestat: Fix optimization in setTableColumnToSensibleDefault
  influxdb: Check before assuming first column to be 'time'

add's info about new template variable interpolation

Improved scrolling experience

reduce content a little bit and highlight mssql and prom heatmap

influxdb: Check before assuming first column to be 'time'

Add gometalinter to CircleCI

remove unused variables detected by varcheck

[skip ci]

add tabs and search filter to new panel control

External auth refactor

Fix performance issue with running bra run for go run build.go build

Specify expected encoding for access/secret key

* master:
  changelog: adds note about closing #11613 and #11602
  fix: sign in link should have target self to trigger full page reload, fixes #11626
  codespell: exclude by words instead of files
  Use sort.Strings() (gosimple)
  Remove unused return value assignment (gosimple)
  Remove unnecessary fmt.Sprintf() calls (gosimple)
  Merge variable declaration with assignment (gosimple)
  Use fmt.Errorf() (gosimple)
  Simplify make() (gosimple)
  Use raw strings to avoid double escapes (gosimple)
  Simplify if expression (gosimple)
  Simplify comparison to bool constant (gosimple)
  Simplify error returns (gosimple)
  Remove redundant break statements (gosimple)

Code simplification (gosimple)