Add Build Performance page under "Troubleshooting"` about hugo-docs-concept HOT 3 OPEN

$ hugo --stepAnalysis --renderToMemory
Started building sites ...
Go initialization:
        258.265545ms (259.985277ms)       249.18 MB     114624 Allocs
initialize:
        325.205µs (261.150696ms)            0.17 MB     278 Allocs
load data:
        10.111382ms (272.069703ms)          1.63 MB     44834 Allocs
load i18n:
        771ns (272.938201ms)        0.00 MB     0 Allocs
read pages from source:
        80.477733ms (353.961149ms)         11.45 MB     109526 Allocs
convert source:
        89.310451ms (443.735408ms)         19.71 MB     164754 Allocs
build Site meta:
        3.768136ms (447.861593ms)           0.32 MB     12092 Allocs
prepare pages:
        100.851742ms (549.879453ms)        40.14 MB     130700 Allocs
render and write aliases:
        8.708986ms (559.015725ms)           0.90 MB     16792 Allocs
render and write pages:
        10.267170333s (10.827670946s)    1675.03 MB     37939564 Allocs
render and write Sitemap:
        21.80858ms (10.85142262s)           1.34 MB     35341 Allocs
render and write robots.txt:
        22.973µs (10.853822419s)            0.00 MB     8 Allocs
render and write 404:
        32.424698ms (10.888415839s)         2.83 MB     67274 Allocs
Built site for language en:
0 of 8 drafts rendered
0 future content
0 expired content
294 regular pages created
259 other pages created
2 non-page files copied
0 paginator pages created
242 tags created
total in 10631 ms

$ hugo benchmark --cpuprofile=cpu.prof
$ go tool pprof `which hugo` cpu.prof
Entering interactive mode (type "help" for commands)
(pprof) top20 -cum
9.52s of 273.97s total ( 3.47%)
Dropped 895 nodes (cum <= 1.37s)
Showing top 20 nodes out of 185 (cum >= 229.11s)
      flat  flat%   sum%        cum   cum%
     0.02s 0.0073% 0.0073%    252.30s 92.09%  text/template.(*Template).Execute
     0.03s 0.011% 0.018%    252.30s 92.09%  text/template.(*Template).execute
     0.02s 0.0073% 0.026%    252.28s 92.08%  html/template.(*Template).Execute
     0.92s  0.34%  0.36%    252.26s 92.08%  text/template.(*state).walk
     0.59s  0.22%  0.58%    251.53s 91.81%  text/template.(*state).evalPipeline
     0.77s  0.28%  0.86%    251.47s 91.79%  text/template.(*state).evalCommand
     0.95s  0.35%  1.20%    250.49s 91.43%  text/template.(*state).evalCall
     0.21s 0.077%  1.28%    250.16s 91.31%  text/template.(*state).evalFunction
     0.69s  0.25%  1.53%    249.79s 91.17%  reflect.Value.Call
     4.60s  1.68%  3.21%    249.76s 91.16%  reflect.Value.call
     0.39s  0.14%  3.35%    248.52s 90.71%  runtime.call64
     0.02s 0.0073%  3.36%    246.71s 90.05%  github.com/spf13/hugo/tpl/tplimpl.(*GoHTMLTemplate).Partial
         0     0%  3.36%    246.70s 90.05%  github.com/spf13/hugo/tpl.(Template).Partial-fm
     0.02s 0.0073%  3.37%    246.62s 90.02%  github.com/spf13/hugo/tpl/tplimpl.(*GoHTMLTemplate).ExecuteTemplateToHTML
     0.01s 0.0037%  3.37%    246.31s 89.90%  github.com/spf13/hugo/tpl/tplimpl.(*GoHTMLTemplate).executeTemplate
     0.14s 0.051%  3.42%    241.23s 88.05%  text/template.(*state).walkIfOrWith
     0.05s 0.018%  3.44%    240.51s 87.79%  text/template.(*state).walkRange
     0.09s 0.033%  3.47%    240.11s 87.64%  text/template.(*state).walkRange.func1
         0     0%  3.47%    234.09s 85.44%  github.com/spf13/hugo/hugolib.(*Site).renderThing
         0     0%  3.47%    229.11s 83.63%  github.com/spf13/hugo/hugolib.(*Site).renderForLayouts