[Core] Message processing: improvement and exploration

[JakiChen]

This is indeed a very time-consuming and unpleasant task, because it is not the core code of the function, but it affects the program's visual experience intentionally or unintentionally.

As a developer:

• You should consider providing basic headers and prompts to guide users to make correct configurations;
• You should try to consider the beauty and readability of the information logged in the terminal (this is a really time-consuming thing, unlike web development, where style adjustments can be made quickly)

I hope that one day Astro's built-in logger can provide a more friendly and beautiful experience.

Current adjustments

• When the configuration directory does not exist, err will be thrown, #10
• For the verification of whether svg is a valid file, currently only a simple verification is done to see if there is an tag. For the time being, we do not plan to put the prompt information online, but return "" to skip invalid svg files. (Because in this way, the type generated by .astro/integrations/astro-svgs/types.d.ts will naturally not contain the SymbolId, but it is not told to the user through the terminal, which is not very friendly) #11