Add .NET 6 & 8 targets and create dotnet tool availability.

[bakerhillpins]

Update the project file to create .NET6/8 outputs that enable dotnet tool support.

From Powershell:

> dotnet tool install BuildBundlerMinifier2022
You can invoke the tool from this directory using the following commands: 'dotnet tool run bundle' or 'dotnet bundle'.
Tool 'buildbundlerminifier2022' (version '2.9.9') was successfully installed. Entry is added to the manifest file D:\Repos\xxx\.config\dotnet-tools.json.
> dotnet tool run bundle
[31m[1mA configuration file called bundleconfig.json could not be found [0m[39m[49m
[33m[1mUsage: BundlerMinifier [[args]] [configPath]
 Each arg in args can be one of the following:
     - The name of an output to process (outputFileName in the configuration file)
         If no outputs to process are specified, all 
     - [ -? | -h | --help | help]        - Shows this help message
         All other arguments are ignored when one of the help switches are included
     - clean                             - Deletes artifacts from previous runs
         All other arguments are ignored when "clean" is included
         Not compatible with "watch"
     - watch                             - Deletes artifacts from previous runs
         Watches files that would cause specified rules to run
         Not compatible with "clean"
     - --no-color                        - Doesn't colorize output
     - [ -? | -h | --help ] to show this help message
 The configPath parameter may be omitted if a bundleconfig.json file is in the working directory
     otherwise, this parameter must be the location of a file containing the definitions for how
     the bundling and minification should be performed.
[0m[39m[49m

[failwyn]

Looks good, I’ll test and merge early next week and publish asap.