Small formatting issues in Batch docs

[mDuo13]

• JSON samples aren't true JSON. The field names must be in double-quote marks (") and integers cannot use hex syntax such as 0x00010000.
• {% raw-partial file="/docs/_snippets/tx-fields-intro.md" /%} is commented out. We have that snippet in this repo now, although it should be included as a {% raw partial="(filename)" /%}.
• In the "Batch Flags" table, the hex values can and should be in code font
• In a few tables, the "JSON Type" values should be in title case, for consistency with our other docs. For example, "String", not "string".
• In a couple tables, the "Internal Type" values use the "ST" prefix inconsistently with other docs and tables. This is also a problem with some other docs on XRPL.org: see Inconsistency in "Internal Type" names XRPLF/xrpl-dev-portal#3121 for recommendations. In short, STAccount → AccountID, and other ST* types should drop the ST prefix.