add: the inline source support

[XiangYyang]

This PR is a refactor version of #56, it also considers the approach of PR #126. And it keeps the original behaviour and reuses existing code wherever possible.

New properties

On the kicanvas-source element,

• name -- provide the original file name
• type -- help determining the file type

Behaviors

• Always use src property if it specify
• name is the original file name, e.g., inline_source.kicad_sch. It's optional and the default value is inline_<NUM>.kicad_XXX, for example, inline_0.kicad_sch, inline_1.kicad_sch, and so on.
• type property can specify file types. It's optional and the default value will be determined by file content and file name.

It works with the existing src attribute. When both are present, all files will be loaded.

<kicanvas-embed controls="full">
    <kicanvas-source name="sch1.kicad_sch">
        (kicad_sch (version 20230121) ...
    </kicanvas-source>
    <kicanvas-source name="sch2.kicad_sch">
        (kicad_sch (version 20230121) ...
    </kicanvas-source>
    <kicanvas-source src="examples/mcu.kicad_sch"></kicanvas-source>
</kicanvas-embed>

[theacodes]

Looks great! Thank you!

[eeyrjmr]

just locally built and integrated with my gitea, works great! thankyou!!