Add recommendation for "escaping" quoted inline script metadata

[ncoghlan]

Issue Description

As described in astral-sh/uv#12303, inline script metadata added naively to a multi-line string will be incorrectly detected as being actual inline script metadata when parsed in accordance with PEP 723 (since the parsing rules are written to be compatible with a basic regex instead of requiring a full Python parser).

https://packaging.python.org/en/latest/specifications/inline-script-metadata/#recommendations should note the problem, and suggest ways to use Python's string quoting flexibility to avoid the misfire.

For example, replacing:

SOURCE_CODE = """
# /// script
# dependencies = ["pydantic", "email-validator"]
# ///
import pydantic

class Model(pydantic.BaseModel):
    email: pydantic.EmailStr

print(Model(email='[email protected]'))
"""

with the following compile time string concatenation:

SOURCE_CODE = ("""
"""
"# /// script"
"""
# dependencies = ["pydantic", "email-validator"]
# ///
import pydantic

class Model(pydantic.BaseModel):
    email: pydantic.EmailStr

print(Model(email='[email protected]'))
""")

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