Add Text Decode + JSON Format

[callzhang]

• I'm the package's author and/or maintainer.
• I have have read the docs.
• I have tagged a release with a semver version number (v1.0.0).
• My package repo has a description and a README describing what it's for and how to use it.
• My package doesn't add context menu entries. *
• My package doesn't add key bindings. **
• Any commands are available via the command palette.
• Preferences and keybindings (if any) are listed in the menu and the command palette, and open in split view.
• If my package is a syntax it doesn't also add a color scheme. ***
• I use .gitattributes to exclude files from the package: images, test files, sublime-project/workspace. (Not
  needed for current minimal payload; can add if requested.)

My package is Sublime Text commands to auto-decode messy text (URL/HTML/unicode/hex/base64/gzip) and fix/pretty-
print JSON, with full-buffer fallback when nothing is selected.

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