dev: upgrade to docsite@v1.5.0, update docsite dev guide

[bobheadxi]

see sourcegraph/docsite#52

[codecov]

Codecov Report

Merging #12874 into main will decrease coverage by 1.66%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main   #12874      +/-   ##
==========================================
- Coverage   51.14%   49.48%   -1.67%     
==========================================
  Files        1446     1432      -14     
  Lines       81057    80460     -597     
  Branches     6561     6595      +34     
==========================================
- Hits        41455    39813    -1642     
- Misses      36037    37086    +1049     
+ Partials     3565     3561       -4     

Flag	Coverage Δ
#go	52.61% <ø> (+<0.01%)	⬆️
#integration	24.27% <ø> (+<0.01%)	⬆️
#storybook	14.12% <ø> (ø)
#typescript	40.67% <ø> (-6.47%)	⬇️
#unit	47.73% <ø> (-0.09%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
browser/src/shared/code-hosts/shared/consts.ts	0.00% <0.00%> (-100.00%)	⬇️
browser/src/shared/code-hosts/github/tooltip.ts	0.00% <0.00%> (-100.00%)	⬇️
browser/src/shared/code-hosts/gitlab/extensions.ts	0.00% <0.00%> (-100.00%)	⬇️
...rowser/src/shared/code-hosts/github/extensions.tsx	0.00% <0.00%> (-100.00%)	⬇️
...er/src/shared/backend/extension-api-conversion.tsx	0.00% <0.00%> (-100.00%)	⬇️
...r/src/browser-extension/web-extension-api/types.ts	0.00% <0.00%> (-100.00%)	⬇️
browser/src/shared/code-hosts/shared/views.ts	0.00% <0.00%> (-98.04%)	⬇️
.../src/shared/code-hosts/shared/codeHostTestUtils.ts	0.00% <0.00%> (-95.24%)	⬇️
...er/src/shared/code-hosts/shared/nativeTooltips.tsx	0.00% <0.00%> (-94.12%)	⬇️
...owser/src/shared/code-hosts/shared/contentViews.ts	0.00% <0.00%> (-93.55%)	⬇️
... and 64 more