Support hashes in requirements.txt

[MarcelBochtler]

When analyzing a requirements.txt file that defines hashes for secure installs

addict==2.4.0 \
    --hash=sha256:249bb56bbfd3cdc2a004ea0ff4c2b6ddc84d53bc2194761636eb314d5cfa5dfc \
    --hash=sha256:b3b2210e0e067a281f5646c8c5db92e99b7231ea8b0eb5f74dbdf9e259d4e494

The Python-Inspector fails with this error:

❯ ~/Projects/oss/python-inspector/venv/bin/python-inspector --python-version 313 --operating-system linux --json-pdt ./inspector-result.json --analyze-setup-py-insecurely --requirement ./requirements.txt --verbose
Resolving dependencies...
Using netrc file /Users/bom1wa3/.netrc
direct_dependencies:
 DependentPackage(purl='pkg:pypi/addict@2.4.0', extracted_requirement='addict==2.4.0 \\\n    --hash=sha256:249bb56bbfd3cdc2a004ea0ff4c2b6ddc84d53bc2194761636eb314d5cfa5dfc \\\n    --hash=sha256:b3b2210e0e067a281f5646c8c5db92e99b7231ea8b0eb5f74dbdf9e259d4e494', scope='install')
environment: Environment(python_version='313', operating_system='linux')
repos:
 PypiSimpleRepository(index_url='https://pypi.org/simple', credentials=None)
Traceback (most recent call last):
  File "/Users/bom1wa3/Projects/oss/python-inspector/venv/lib/python3.11/site-packages/packvers/requirements.py", line 102, in __init__
    req = REQUIREMENT.parseString(requirement_string)
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/bom1wa3/Projects/oss/python-inspector/venv/lib/python3.11/site-packages/pyparsing/core.py", line 1141, in parse_string
    raise exc.with_traceback(None)
pyparsing.exceptions.ParseException: Expected string_end, found '\'  (at char 14), (line:1, col:15)

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/Users/bom1wa3/Projects/oss/python-inspector/src/python_inspector/resolve_cli.py", line 259, in resolve_dependencies
    resolution_result: Dict = resolver_api(
                              ^^^^^^^^^^^^^
  File "/Users/bom1wa3/Projects/oss/python-inspector/src/python_inspector/api.py", line 283, in resolve_dependencies
    resolution, purls = resolve(
                        ^^^^^^^^
  File "/Users/bom1wa3/Projects/oss/python-inspector/src/python_inspector/api.py", line 368, in resolve
    requirements = list(
                   ^^^^^
  File "/Users/bom1wa3/Projects/oss/python-inspector/src/python_inspector/api.py", line 484, in get_requirements_from_direct_dependencies
    req = Requirement(requirement_string=dependency.extracted_requirement)
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/bom1wa3/Projects/oss/python-inspector/venv/lib/python3.11/site-packages/packvers/requirements.py", line 104, in __init__
    raise InvalidRequirement(
packvers.requirements.InvalidRequirement: Parse error at "'\\\n    --'": Expected string_end