add page support

[wang0618]

No description provided.

[codecov-commenter]

Codecov Report

Merging #427 (3e647e7) into dev (fc99bde) will decrease coverage by 1.13%.
The diff coverage is 50.84%.

@@            Coverage Diff             @@
##              dev     #427      +/-   ##
==========================================
- Coverage   84.36%   83.23%   -1.14%     
==========================================
  Files          26       26              
  Lines        3288     3393     +105     
==========================================
+ Hits         2774     2824      +50     
- Misses        514      569      +55     

Impacted Files	Coverage Δ
pywebio/output.py	85.83% <32.35%> (-4.28%)	⬇️
pywebio/session/base.py	64.00% <34.88%> (-15.52%)	⬇️
pywebio/session/coroutinebased.py	86.09% <70.00%> (-0.35%)	⬇️
pywebio/session/threadbased.py	89.85% <81.81%> (-0.60%)	⬇️
pywebio/session/__init__.py	91.93% <85.71%> (-0.57%)	⬇️
pywebio/io_ctrl.py	78.64% <90.00%> (+0.64%)	⬆️
pywebio/exceptions.py	100.00% <100.00%> (ø)
pywebio/pin.py	90.72% <100.00%> (+0.09%)	⬆️
pywebio/utils.py	85.41% <0.00%> (+0.52%)	⬆️

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