Adding examples for common encodings, table of all supported encoding

[Ian-Fogelman]

PR for: #5686

• Adding a full alphabetized table to /core_extensions/encodings.md for all encodings supported in DuckDB.
• Adding link to data/csv/overview.md to link back to master supported encoding table.
• Nit monospace's applied on keywords.
• Added examples of the top encodings supported to Usage on /core_extensions/encodings.md.
• I did not test all 1042 encodings, but did test the usage examples, for details on testing procedure see My Gist.

Links:

Stable:

• http://localhost:4000/docs/stable/core_extensions/encodings.html
• http://localhost:4000/docs/stable/data/csv/overview.html

Preview:

• http://localhost:4000/docs/preview/core_extensions/encodings.html
• http://localhost:4000/docs/preview/data/csv/overview.html