Add utf-8 supporting + minified + tests

[username1565]

Browser web-version: Added file sha256_unicode.js - sha256 function with UTF-8 supporting. Added file sha256_unicode.min.js - minified version, after minify, using online javascript minifiers. Added page sha256_utf8.html - demo page. Added page test.html - with tests ASCII and UTF-8. Source code of test.html added to README.md

All files and scripts (sha256.js and sha256.min.js too), are encoded as UTF-8 text (with BOM), now.

Change index.html:

• meta-tag with utf-8 encoding - added.
• added size in bytes for sha256.min.js (852 bytes).
• Link to sha256_utf8.html - added.
• Description for textarea - added.
• The title tooltip for input textarea.
• Upper-case checkbox and function change_case() - added.
• eventlistener oninput - added. Now hash updating on input value.
• Run hash-function, when page loaded.
• Description for code - added.

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Now, you can minify this, and merge.

[username1565]

See: https://username1565.github.io/sha256/