Add DisplaySize configuration for 64x32 displays

[carlossless]

• [x] Check that you've added documentation to any new methods
• [x] Rebase from master if you're not already up to date
• [x] Add or modify an example if there are changes to the public API
• [x] Add a CHANGELOG.md entry in the Unreleased section under the appropriate heading (Added, Fixed, Changed, etc)
• [x] Run rustfmt on the project with cargo fmt --all - CI will not pass without this step
• [x] Check that your branch is up to date with master and that CI is passing once the PR is opened

PR description

Adding a predefined configuration for 64x32 displays, commonly marketed as "0.49" OLED display" like this panel or this module.

[carlossless]

@jamwaffles seems like the build is failing, but it's not due to the changes in this PR.

[carlossless]

@jamwaffles yes, I have the included configuration running in my setup, so I can confirm that it's working as expected.

For additional reference, other drivers have implemented the same offset: https://github.com/olikraus/u8g2/blob/master/csrc/u8x8_d_ssd1306_64x32.c#L159

[jamwaffles]

Released in 0.7.1.