Add exclude to config

[MikeKalinowski]

This PR partially solves issue #39 by adding option to exclude files. To fully resolve that issue, option to create paths with globs is needed.

This PR addresses three places where file paths are checked. Please take a look if I haven't missed anything. Addressed places are:

• IDE check and cli tsc-strict use isFileStrict.ts to decide which files to check
• cli update-strict-comments checks files at few different stages. This implementation checks them during first search for the files (index.ts -> findStrictFiles). So files that are excluded will not later go through the process of adding/removing comments.

The priority of checks according to new isFileStrict.ts will be:

1. ts strict ignore comment
2. ts strict comment
3. exclude
4. include
   To give an example, if file is both in include and exclude, it will be excluded. If it has @ts-strict and exclude, it will be included.

[MikeKalinowski]

This is heavily based on check for 'paths' in isFileStrictByPath.ts, but there is a small difference in guard clause

[MikeKalinowski]

Let me know if you want me to merge them into one function

[a7madgamal]

I could really use this! I wanted to open an issue so finding a PR ready is fantastic!
how can I help or what's missing here?