fix: space character problem when parsing content-type

[zruhao]

Solve the problem that the response cannot be formatted when the content-type contains spaces, such as content-type: application/json ; charset=utf-8

[Grueslayer]

@zruhao As your fix does not harm kulala, your example is not valid. Since the first RFC 822, there is no space allowed

Content-Type := type "/" subtype *[";" parameter] 

type :=          "application"     / "audio" 
          / "image"           / "message" 
          / "multipart"  / "text" 
          / "video"           / x-token 

x-token := <The two characters "X-" followed, with no 
           intervening white space, by any token> 

subtype := token 

parameter := attribute "=" value 

attribute := token 

value := token / quoted-string 

token := 1*<any CHAR except SPACE, CTLs, or tspecials> 

tspecials :=  "(" / ")" / "<" / ">" / "@"  ; Must be in 
           /  "," / ";" / ":" / "\" / <">  ; quoted-string, 
           /  "/" / "[" / "]" / "?" / "."  ; to use within 
           /  "="                        ; parameter values