docs: rewrite readme, rfcs, and contributing (#555)

* docs: rewrite README, RFCs, and CONTRIBUTING
* docs: fix Linux storage labels in RFC-006 (Opera/Vivaldi swapped)

Author: moonD4rk

CONTRIBUTING.md

@@ -1,30 +1,73 @@
 # Contributing to HackBrowserData
 
-We appreciate your interest in contributing to the HackBrowserData! This document provides some basic guidelines for contributors.
+We appreciate your interest in contributing to HackBrowserData! This document provides guidelines for contributors.
 
 ## Getting Started
 
-- Always base your work from the `dev` branch, which is the development branch with the latest code.
+- Always base your work from the `main` branch.
 - Before creating a Pull Request (PR), make sure there is a corresponding issue for your contribution. If there isn't one already, please create one.
-- Include the problem description in the issue.
+
+## Go Version Constraint
+
+This project **must build with Go 1.20** to maintain Windows 7 support. This is enforced by CI.
+
+- Do **not** use features from Go 1.21+ (e.g., `log/slog`, `slices`, `maps`, `cmp` packages)
+- Do **not** bump the `go` directive in `go.mod` beyond `go 1.20`
+- `modernc.org/sqlite` is pinned at v1.31.1 (v1.32+ requires Go 1.21)
+
+## Development Commands
+
+```bash
+# Build
+go build ./cmd/hack-browser-data/
+
+# Test
+go test ./...
+
+# Lint (requires golangci-lint v2)
+golangci-lint run
+
+# Format
+gofumpt -l -w .
+goimports -w -local github.com/moond4rk/hackbrowserdata .
+
+# Spelling check
+typos
+```
 
 ## Pull Requests
 
 When creating a PR, please follow these guidelines:
 
 - Link your PR to the corresponding issue.
-- Provide context in the PR description to help reviewers understand the changes. The more information you provide, the faster the review process will be.
-- Include an example of running the tool with the changed code, if applicable. Provide 'before' and 'after' examples if possible.
+- Provide context in the PR description to help reviewers understand the changes.
+- Include 'before' and 'after' examples if applicable.
 - Include steps for functional testing or replication.
 - If you're adding a new feature, make sure to include unit tests.
 
+### Commit Message Convention
+
+Use [Conventional Commits](https://www.conventionalcommits.org/) format:
+
+```
+feat: add support for new browser
+fix: resolve cookie decryption on Windows
+chore: update dependencies
+docs: improve RFC documentation
+refactor: simplify profile discovery logic
+test: add extraction tests for Firefox
+```
+
 ## Code Style
 
-Please adhere to the existing coding style for consistency.
+- **Platform code**: use build tags (`_darwin.go`, `_windows.go`, `_linux.go`)
+- **Error handling**: use `fmt.Errorf("context: %w", err)` for wrapping; do not ignore errors unless it is deliberate best-effort cleanup (e.g. `Close`/`Remove`)
+- **Naming**: follow Go conventions
+- **Tests**: use `t.TempDir()` for filesystem tests
+- **Architecture**: see `rfcs/` for design documents
 
 ## Questions
 
-If you have any questions or need further guidance, please feel free to ask in the issue or PR, or [reach out to the maintainers](mailto:i@moond4rk.com). We will reply to you as soon as possible.
+If you have any questions or need further guidance, please feel free to ask in the issue or PR, or [reach out to the maintainers](mailto:me@moond4rk.com). We will reply to you as soon as possible.
 
 Thank you for your contribution!
-