feat: free to name markdown files

[fjc0k]

close: #433, #380, #344, #307

free to name markdown files, e.g.

JS 手册.md
so, what?.md
hello world!.md

[x8x]

@fjc0k Amazing! Could this also fix #310 ?
@ulivz This is big! Any chances to get this merged into 0.9 ?
Thank to both of you!

[ulivz]

Thanks for the great work, but the implementation is too complex, let's go #473 instead.