Add TS example of handling POST data from a router.

[technosophos]

Content must go through a pre-merge checklist.

Pre-Merge Content Checklist

This documentation has been checked to ensure that:

• The title, template, and date` are all set
• Does this PR have a new menu item (anywhere in templates/*.hbs files) that points to a document .md that is set to publish in the future? If so please only publish the .md and .hbs changes in real-time (otherwise there will be a menu item pointing to a .md file that does not exist)
• File does not use CRLF, but uses plain LF (hint: use cat -ve <filename> | grep '^M' | wc -l and expect 0 as a result)
• Has passed bart check
• Has been manually tested by running in Spin/Bartholomew (hint: use PREVIEW_MODE=1 and run npm run styles to update styling)
• Headings are using Title Case
• Code blocks have the programming language set to properly highlight syntax and the proper copy directive
• Have tested with npm run test and resolved all errors
• Relates to an existing (potentially outdated) blog article? If so please add URL in blog to point to this content.

[technosophos]

Huge thanks to @bacongobbler for finding a couple of potential fixes.

[karthik2804]

@technosophos this looks great. Out of curiosity, would it be better if we add an example of using the router with the spin-component-route along with it and make it a more general example of the usage of the router?

[technosophos]

@karthik2804 Yeah, that is a good idea. Let me add that.

[technosophos]

Okay, @karthik2804 -- updated in both