rename the name variable on custom tags to tag_name.

[jwoertink]

Purpose

Fixes #1307

Description

If you're building a front-end app and need your custom tags to take a name prop, this would conflict with the custom tag's name argument.

tag("widget", name: "Alert")

#=> Error: argument 'name' already specified

This PR fixes it by changing the argument to tag_name.

Checklist

• - An issue already exists detailing the issue/or feature request that this PR fixes
• - All specs are formatted with crystal tool format spec src
• - Inline documentation has been added and/or updated
• - Lucky builds on docker with ./script/setup
• - All builds and specs pass on docker with ./script/test