Refactor static pages code; Ensure static pages are read with project `encoding`

[ZedThree]

• Try to use pathlib.Path more consistently in PageNode/pagetree code
• Ensure static pages are read using the project's encoding setting
• Add some static pages to the example project
  • The .gitignore was set to ignore these files, so removed those and added some more common python/emacs/linux patterns

Fixes #518

@zoziha If you're able, please could you try this branch and check that it fixes your issue?

[zoziha]

This PR fixes that issue, thank you for this fix, @ZedThree .

I tested this PR locally, and everything worked fine because of the encoding configuration applied to static pages. I tested the following:

1. Default: encoding:utf-8 is not declared in the FORD.md project file. ✔

   UTF-8 encoded Fortran source code and static pages success expectedly. GBK encoded Fortran source code and static pages fail expectedly.

2. Declare encoding:utf-8 in the FORD.md project file. ✔

   UTF-8 encoded Fortran source code and static pages success expectedly. GBK encoded Fortran source code and static pages fail expectedly.

3. Declare encoding:gbk in the FORD.md project file. ✔

   UTF-8 encoded Fortran source code and static pages fail expectedly. GBK encoded Fortran source code and static pages success expectedly.

The above results are as expected.

PS. The FORD.md project file with non-ASCII code should to be UTF-8 encoded, otherwise the build fails.

[ZedThree]

Great, thank you @zoziha!

I would like to be able to relax your last point about the project file needing to be in UTF-8, but I'll try to address that in the future