feat: include JSON schema to index.html

[danielpeintner]

fixes #1004

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[sebastiankb]

if I see this correctly, the new terms are missing in the JSON Schema

• multipleOf (integer and number schema)
• minLength + maxLength (sting schema)
• contentEncoding + contentMediaType (DataSchema)
• ComboSecurityScheme with oneOf and allOf

[egekorkan]

Combo is introduced in #944 and it is available. Providing fix for the other ones

[danielpeintner]

if I see this correctly, the new terms are missing in the JSON Schema

I think the updates to JSON Schema should probably be another follow-up PR. This PR purely includes the file as is...

[sebastiankb]

@ashimura
I will merge this PR in the hope that it will be included in the FPWD version.