Continuation of #107 UnsupportedEncodingException

**Describe the bug**

We have seen the same customer come back with a re-occurrence of #107 but this time using different unsupported code page iso-8859-8-i ( https://en.wikipedia.org/wiki/ISO-8859-8-I )

I think @jmehrens comment in #107 about being more flexible with lookups is likely to be a better solution than adding another mapping, perhaps with the option to specify a fallback code page where the name is not recognized.

We're happy to work on a PR for this but it might take some time to get the contributor agreements signed off our side and we would like guidance on the preferred approach. Specifically when building the suggested table based lookup what is the expected source of charset names?

Would it be acceptable to add something like icu4j as a dependency to help with enumerating charset aliases?

**To Reproduce**
Create a mail with 'Content-Type: text/html; charset="iso-8859-8-i"
Invoke getContent() API on the email and it fails.

**Expected behavior**
To process the email even if it uses charset="iso-8859-8-i"

**Screenshots**
If applicable, add screenshots to help explain your problem.

**Desktop (please complete the following information):**

- OS: Linux
- Browser n/a
- Version 2.0.3

**Smartphone (please complete the following information):**

n/a

**Mail server:**

- Protocol being used: pop3
- Vendor/product: outlook
- Mail service URL: customer onPrem

**Additional context**
Add any other context about the problem here.