feat: handle checkJs property if set in tsconfig

[tkgroot]

if the tsconfig.json contains the property checkJs: true, javascript files are not checked by tsc-files since the files filters do ignore file extensions other than ts and tsx. However, since checkJs should include all valid javascript file extensions, it is expected that it will respect the setting of the tsconfig.json and take the additional file extensions js, cjs and mjs into account.

[jonasgeiler]

Same problem as in #71: I don't believe you have to check if allowJs or checkJs are enabled. It's probably fine to just always look for .js files and .ts files in the CLI arguments, since you wouldn't pass JS files to tsc-files if you didn't want tsc-files to check them, right? Same as you wouldn't give JS files to tsc if you didn't want tsc to check them.

At least that's what I did in my fork at @jonasgeiler/tsc-files.

Also kind of a duplicate of #55.