Use null terminator for masking inline ignore

[caitlinelfring]

Please check if the PR fulfills these requirements

• The commit message follows our guidelines
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

What kind of change does this PR introduce? (Bug fix, feature, docs update, ...)
Bug fix

What is the current behavior? (You can also link to an open issue here)
Use the unicode.ReplacementChar � to mask any inline ignores so they don't result in a "finding". This is actually a three byte symbol and causes the matcher to return incorrect and out of bound indexes

What is the new behavior (if this is a feature change)?
Switch to using a single byte character to mask inline ignores (null terminator - http://en.wikipedia.org/wiki/Null_character). The goal is to use something that wouldn't trigger any findings

Does this PR introduce a breaking change? (What changes might users need to make due to this PR?)
No

Other information:
Fixes #109

[codecov]

Codecov Report

Merging #111 (76b974a) into main (4c46b2f) will not change coverage.
The diff coverage is 100.00%.

❗ Current head 76b974a differs from pull request most recent head 93b586d. Consider uploading reports for the commit 93b586d to get more accurate results

@@           Coverage Diff           @@
##             main     #111   +/-   ##
=======================================
  Coverage   96.22%   96.22%           
=======================================
  Files          20       20           
  Lines         583      583           
=======================================
  Hits          561      561           
  Misses         13       13           
  Partials        9        9           

Impacted Files	Coverage Δ
pkg/rule/rule.go	93.75% <100.00%> (ø)

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