A bit late, but the current link points to a non-existant page.

Fixes #18873.

1. Found the .NET foundation badge at https://img.shields.io/badge/.NET%20Foundation-blueviolet.svg
2. Added to badge collection.

* Badges, badges! (Licence, Help wanted, Good first issue, Chat)

* Use correct links

- part of #29475
- primarily involves updating links to this repo

nit: Remove broken links to old Travis environments (that happen to mention 'master')

* Added the link to the IssueManagementPolicies document

* Updated to reference the Triage Process

Except aspnet/AspNetCore-Internal.

Prior to reorganization, this source code was found in https://github.com/aspnet/Identity/tree/4a717c85635671e04c8691fe3c125a77ee46d32a

Prior to reorganization, this source code was found in https://github.com/aspnet/Identity/tree/4b3d8e5106158fb29da33c8e14134ed168a5e880

Prior to reorganization, this source code was found in https://github.com/aspnet/Identity/tree/fa3cfd08eb6af819adc5fef2d9b603638c4b4b3b

Prior to reorganization, this source code was found in https://github.com/aspnet/Localization/tree/0bcac31dd705fb9db60723f5d7eaeffb728358f5

Prior to reorganization, this source code was found in https://github.com/aspnet/BasicMiddleware/tree/1de636cd18309070792b68888ca29c8b85fac98b

Prior to reorganization, this source code was found in https://github.com/aspnet/Razor/tree/582f3f867eeb8fca00e6b328faf7665c9a98476c

Prior to reorganization, this source code was found in https://github.com/aspnet/MvcPrecompilation/tree/3cd4de8af8322b90e62a5818ece90428e2dc933b

Prior to reorganization, this source code was found in https://github.com/aspnet/Mvc/tree/c9887e027a97b07a3ae7699112b9a2620a36e553

Prior to reorganization, this source code was found in https://github.com/aspnet/SignalR/tree/c852bdcc332ffb998ec6a5b226e35d5e74d24009

Prior to reorganization, this source code was found in https://github.com/aspnet/Razor/tree/8ba0a894256e4b5c5385db9b5aac32fdbd046f3a

Prior to reorganization, this source code was found in https://github.com/aspnet/MvcPrecompilation/tree/032768b063a768559c8dfaea0d06380da77307ae

Prior to reorganization, this source code was found in https://github.com/aspnet/Mvc/tree/a6199bbfbab05583f987bae322fb04566841aaea

Prior to reorganization, this source code was found in https://github.com/aspnet/SignalR/tree/d0bcdf3dd92afba858fca2871535faf4594c81de

Prior to reorganization, this source code was found in https://github.com/aspnet/Razor/tree/fd4572874e41ca3af803b0b2c71955505dd4bde5

Prior to reorganization, this source code was found in https://github.com/aspnet/MvcPrecompilation/tree/617586a984b1eff9ca0ca8126dd0b1dab2ea16f2

Prior to reorganization, this source code was found in https://github.com/aspnet/Mvc/tree/5a4fd3e792e75619e3b1de069fabdf87d2cd0983

Prior to reorganization, this source code was found in https://github.com/aspnet/SignalR/tree/bc148a07244a451e48b7e0efdf16db8f69f788ff

Prior to reorganization, this source code was found in https://github.com/aspnet/Security/tree/26d27d871b7992022c082dc207e3d126e1d9d278

Prior to reorganization, this source code was found in https://github.com/aspnet/Routing/tree/c28c7dea4e866ec5a0d33f0e290bc49baadb1c85

Prior to reorganization, this source code was found in https://github.com/aspnet/ResponseCaching/tree/12395b4d1c03e49134704679f94af6f328a7e1d5

Prior to reorganization, this source code was found in https://github.com/aspnet/HttpSysServer/tree/d4f588658218ef59c8ae14261e323efa6d8a8156