Nuspec inspector reloads old content when switching window focus

[chrisfromwork]

Description

It seems like there is some unexpected UI behavior when changing window focus for the nuspec inspector window. I think that removing focus from the window results in the nuspec inspector reloading the file content, which overwrites any changes a user has made. This can make for a difficult editing experience.

In my repro, I am attempting the following:

1. Create a new nuspec file
2. Change some fields such as creator/owner
3. Change windows to a web browser to get the license url
4. Change windows back to the nuspec inspector

Observed:
5. Nuspec inspector reloads the file content and my initial changes (not yet saved) are overwritten to preexisting the file content

Expected:
5. Nuspect inspector keeps my changes not yet saved

• NuGet Package: [What is the name and version of the NuGet package you are installing?]
• NuGetForUnity Version: 1.0.3
• Unity Version: 2018.3.3f1
• Operating System: Windows 10