Add OpenWhispr easy setup installer and companion files

Single-file bash installer (setup-openwhispr.sh) with distro detection,
dependency installation, STT/AI cleanup provider selection, API key
management, and first-run launch. Includes README, LICENSE (MIT),
CHANGELOG, .gitignore, ShellCheck CI, issue templates, PR template,
and GitHub setup guide.

https://claude.ai/code/session_01XKYC1basxdwtHy71tky7xm

.gitignore

@@ -0,0 +1,15 @@
+# OS
+.DS_Store
+Thumbs.db
+
+# Editor
+*.swp
+*.swo
+*~
+.vscode/
+.idea/
+
+# Temp
+/tmp/
+*.bak
+*.tmp