Add configuration and rule suppression support

[Pavithran-R-A]

Problem

There is currently no way to configure SetupSentry behavior or suppress specific rules. Users may have legitimate reasons to ignore certain findings (e.g., documentation examples that intentionally show dangerous commands).

Proposed Scope

Allow users to configure SetupSentry via:

• A config file (e.g., .setupsentryrc.json or a setupsentry key in package.json)
• CLI flag to suppress specific rules (e.g., --ignore SS001)
• Per-file or per-pattern suppression comments (e.g., )

Files/Components

• New config loading module
• CLI argument handling in src/cli.ts
• Suppression logic in src/engine.ts
• Tests for config loading and suppression behavior
• README documentation

Acceptance Criteria

• Config file support (at least one format)
• CLI --ignore flag to suppress rules by ID
• Inline suppression comment support in markdown
• Tests for all suppression mechanisms
• README documents configuration options
• All existing tests still pass