Allow units for page size

[nikischin]

In addition to #2771 I also implemented the support for units "in", "cm", "mm" to the <Page/> size attribute.

Includes the fixes for the dpi from #2771 already but had to be a bit rewritten.

implements #2008
fixes #2885

Some background about this and also #2771:
The PDF spec doesn't really have DPI and always expects the unit to be user points which always expects points in an PDF to be 1/72 of an inch. So any unitless value in a PDF always should be considered a user point. The dpi setting then should represent a user unit which defaults to 72 dots per inch and can change this conversion to anything else.

Please check out more details to this here or here

The thing with PDF is, you always want to have a font set to 12pt to be the same size no matter what dpi setting you have. You can check on Adobe Indesign and create two pdfs, one with 72dpi and one with 300dpi, and in both the font will have the same size (relative to the page size) if set to 12pt (which equals 12 user points). This was not working before the fix and was therefore super confusing. Why should the complete layout of the page change when I change the dpi setting?

Please note that debug mode also represents the user points and not pixels.

Expected behavior

• A page with "A4" will result in 595 x 841 points no matter what dpi is set

• A page with {{width: "210mm", height: "297mm"}} will result in 595 x 841 points no matter what dpi is set

• A page with {{width: 595, height: 841 }} will result in 595 x 841 points no matter what dpi is set

• A page with {{width: "595px", height: "841px" }} will result in 595 x 841 points on 72 dpi, but only 142 x 202 points on 300dpi

• A element with a width of 590 points will almost fill the page for a A4 page no matter what dpi

• A element with a width of "99vw" will almost fill the page for a A4 page no matter what dpi

• A element with a width of "590px" will almost fill the page for a A4 page on 72dpi but will only fill about 1/4 or 1/5 on 300dpi

[changeset-bot]

🦋 Changeset detected

Latest commit: 0554c1d

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 6 packages

Name	Type
@react-pdf/stylesheet	Major
@react-pdf/layout	Major
@react-pdf/renderer	Patch
@react-pdf/examples	Patch
@react-pdf/e2e-node-cjs	Patch
@react-pdf/e2e-node-esm	Patch

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

[nikischin]

Thank you for merging #2771 @diegomura, in addition I also merged the branch and prepared this PR.

[nikischin]

Could you have a look on this please @diegomura? Thank you so much!