feat: add optional kw-arg 'filtered=True' in Name

[linw1995]

It supports a new syntax like '$.goods[*].?category'.
Allow user to disable default behavior that filters the missing fields.

Fixes #40

This PR is still in development progress, please use it carefully.

❯ cat example.json 
{
    "goods": [
        {"price": 100, "category": "Comic book"},
        {"price": 200, "category": "magazine"},
        {"price": 200, "no category": ""}
    ],
    "targetCategory": "book"
}
❯ jp -f example.json '$.goods[*].?category'
[
  "Comic book",
  "magazine",
  null
]

[codecov]

Codecov Report

Merging #41 (291b643) into master (3442ead) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##            master       #41   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            6         6           
  Lines          561       580   +19     
  Branches        75       107   +32     
=========================================
+ Hits           561       580   +19     

Impacted Files	Coverage Δ
jsonpath/core.py	100.00% <100.00%> (ø)
jsonpath/transformer.py	100.00% <100.00%> (ø)

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