Add rule for warning about backticks that look like line-continuations but are not

[AndrewGaspar]

This is in response to #423.

Let me know if there are any anti-patterns here. Examining the text directly feels a little weird here, but I believe that escaped whitespace isn't reflected in any way in the AST, so I need to look at the text directly.

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[raghushantha]

Hi Andrew. Thank you for the new rule and the test cases. Changes look good.

Please fix this failing test before we can merge the PR:
Describing Test Name parameters
Context When used correctly
[+] works with 1 name 275ms
[+] works for DSC Rule 17ms
[+] works with 3 names 21ms
[-] Get Rules with no parameters supplied 181ms
Expected: {38}
But was: {39}
59: $defaultRules.Count | Should be 38
at , C:\projects\psscriptanalyzer\Tests\Engine\GetScriptAnalyzerRule.tests.ps1: line 59

[AndrewGaspar]

Oh yeah, sorry about that. I'll fix that tonight. Does that count just need to stay in sync with the number of rules in ScriptAnalyzer?

[raghushantha]

Yes.

[AndrewGaspar]

Tests fixed

[raghushantha]

Great.. Thanks!

[raghushantha]

Need to update the rule documentation. I will take care of that
https://github.com/PowerShell/PSScriptAnalyzer/tree/development/RuleDocumentation