docs: improve placeholder text of the route header override

[okaybase]

Please answer these questions before submitting a pull request, or your PR will get closed.

Why submit this pull request?

1. Improve placeholder text of the route header override.
2. Improve label of the route match parameter value.
3. Correct the title for creating route in the file search-route.spec.js.
4. Correct the spelling of some words.

• Bugfix
• New feature provided
• Improve performance
• Improve document
• Backport patches

What changes will this PR take into?

Please update this section with detailed description.

Related issues

fix/resolve

Checklist:

• Did you explain what problem does this PR solve? Or what new features have been added?
• Have you added corresponding test cases?
• Have you modified the corresponding document?
• Is this PR backward compatible? If it is not backward compatible, please discuss on the mailing list first

[netlify]

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[iamayushdas]

Why to change this, Value is fine IMO

[okaybase]

Yes, without the Parameter is also ok here. @iamayushdas
Parameter is added only to be consistent with the Chinese version.

[iamayushdas]

cc @juzhiyuan have a look here

[okaybase]

Thanks very much for your careful review! @iamayushdas

[codecov-commenter]

Codecov Report

Merging #1973 (7e6145f) into master (1e55aa3) will decrease coverage by 0.06%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master    #1973      +/-   ##
==========================================
- Coverage   64.01%   63.95%   -0.07%     
==========================================
  Files         122      122              
  Lines        3154     3154              
  Branches      753      753              
==========================================
- Hits         2019     2017       -2     
- Misses       1135     1137       +2     

Flag	Coverage Δ
frontend-e2e-test	63.95% <0.00%> (-0.07%)	⬇️

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

Impacted Files	Coverage Δ
.../src/pages/Route/components/Step1/ProxyRewrite.tsx	94.44% <ø> (ø)
web/src/pages/Route/components/Step3/index.tsx	51.85% <0.00%> (ø)
web/src/helpers.tsx	68.85% <0.00%> (-3.28%)	⬇️

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[okaybase]

Please take time to review, thanks! @juzhiyuan @nic-chen