Update Unity.gitignore

[Domiurk]

Add .idea directory

Reasons for making this change:

TODO

Links to documentation supporting these rule changes:

TODO

If this is a new template:

• Link to application or project’s homepage: TODO

[EudenDev]

For IntelliJ suite I found this:

# Common IntelliJ Platform excludes

# User specific
**/.idea/**/workspace.xml
**/.idea/**/tasks.xml
**/.idea/shelf/*
**/.idea/dictionaries
**/.idea/httpRequests/

# Sensitive or high-churn files
**/.idea/**/dataSources/
**/.idea/**/dataSources.ids
**/.idea/**/dataSources.xml
**/.idea/**/dataSources.local.xml
**/.idea/**/sqlDataSources.xml
**/.idea/**/dynamic.xml

# Rider
# Rider auto-generates .iml files, and contentModel.xml
**/.idea/**/*.iml
**/.idea/**/contentModel.xml
**/.idea/**/modules.xml
**/.idea/misc.xml

Source?: https://github.com/JetBrains/resharper-rider-samples/blob/master/.gitignore

Theres also this but I haven't tried it:

# Ignore only specific Rider files/directories
# For syntax see: https://stackoverflow.com/a/14422549/12124
/.idea/*
!/.idea/.idea.*
/.idea/.idea.*/*
!/.idea/.idea.*/.idea
/.idea/.idea.*/.idea/*
!/.idea/.idea.*/.idea/runConfigurations

Source: https://www.tjrobinson.net/2019-04-28-a-gitignore-file-for-excluding-rider-idea-directories-except-runconfigurations/