[Schema][Server] Add support for icons and website url

[chr-hertel]

Close #136

[lvluoyue]

I discovered that the lack of Attribute support will prevent obtaining the tools list.

Typed property Mcp\\Schema\\Tool::$icons must not be accessed before initialization

I have an idea: we can extract the icon into an annotation (meta should also be able to use this method), not sure if it's feasible.

[chr-hertel]

1. you are right, the attributes should support this as well
2. how did you run into the error? cannot reproduce with an example 🤔

[lvluoyue]

1. you are right, the attributes should support this as well
2. how did you run into the error? cannot reproduce with an example 🤔

I used Discovery Cache, and after clearing the cache, it worked normally. It seems that the cache was not refreshed, which caused the issue.

[lvluoyue]

1. you are right, the attributes should support this as well
2. how did you run into the error? cannot reproduce with an example 🤔

I used Discovery Cache, and after clearing the cache, it worked normally. It seems that the cache was not refreshed, which caused the issue.

[chr-hertel]

That cache hiccup makes sense & and #142 should address your finding