feat: allow options to customize pattern and hash length

[metonym]

Closes #46 , closes #45

---

Backwards compatible API change that allows the pattern RegExp and hash length to be customized.

Example:

hash({
  path: 'public', // default is `""`
  pattern: new RegExp(/\[oh-my-hash.*]/g), // default is `new RegExp(/\[hash.*]/g)`
  hashLength: 8 // default is `20`
})

- script.[oh-my-hash].js
+ script.b0dcc67f.js

TODO

• update/add unit tests
• update/add integration tests
• ideally add an end-to-end standalone example
• update documentation

[metonym]

@frederikhors

Added an integration test for a custom pattern and hash length:

hash({
  pattern: new RegExp(/\oh-my-hash/),
  hashLength: 8,
})

With a custom RegExp pattern, you are not required to use square brackets.

- <script src="script.oh-my-hash.js"></script>
+ <script src="script.b0dcc67f.js"></script>

[frederikhors]

Do you really like "oh-my-hash", don't you?! 😄 LOL