Update the documentation

[JSYOU]

What’s the problem you're trying to solve

With the increase of users and version updates, the current documentation is no longer sufficient to meet the user's needs and requires an update.

Describe the solution you’d like

The set-sampler section does not mention that incomplete parameter settings can cause the server to fail during the startup phase, for example, if we would like to check data from context.req.xxx like below:

-- We use the req in sql file
select  
*,  
{{ context.req.method }} as "req-method",
{{ context.req.url }} as "req-url"
from "artists" where 
ConstituentID = {{ context.params.id }}
and
{{ context.req.method }} = 'GET'

# API Schema
urlPath: /artist/:id
request:
  - fieldName: id
    fieldIn: path
    description: constituent id
    validators:
      - required
sample:
  req:
    method: GET
    url: 'localhost:3000'
  parameters:
    id: '1'
  profile: duck
profile: duck

Then we should also set the req in the sample.

Otherwise the install-vulcansql-cli section has different instructions for Windows users, etc.