fix: exclude URL(http/https/ftp) patterns from markdown-it-include target

[fukusuket]

Hello, Thank you so much for great tool :)
The issue #181 also occurred in my environment(win10/macOS/vscode-markdown-pdf 1.5.0), so I fixed it.

What Changed

Changed the regular expression targeted by markdown-it-include

• To prevent the following case's ENOENT: no such file or directory error
  • Error: ENOENT: no such file or directory, open 'd:\xx\Ljava\lang\String;' #181 (comment)

About the changed regular expression in this PR

before fix

All cases containing URL link patterns are targets of markdown-it-include as follows:

after fix

URL link patterns are not targets of markdown-it-include as follows: (By using a negative lookahead regular expression)

I would appreciate it if you could review.
Thanks again maintaining great tool !

[fukusuket]

Test (issue #181)

Environment

• macOS Sonoma 14.2.1
• VSCode 1.85.1

before fix

I have confirmed that the reproduction of the problem before fixing it as follows.

after fix

I have confirmed that there are no errors when exporting pdf and html as follows.

[fukusuket]

Test (other pattern)

after fix

I have confirmed that there are no errors when exporting pdf and html as follows.