docs: refine KCLVM readme

[Peefy]

1. Does this PR affect any open issues?(Y/N) and add issue references (e.g. "fix #123", "re #123".):

• N
• Y

re #165. Refine KCL readme badges and documents.

2. What is the scope of this PR (e.g. component or file name):

3. Provide a description of the PR(e.g. more details, effects, motivations or doc link):

• Affects user behaviors
• Contains syntax changes
• Contains variable changes
• Contains experimental features
• Performance regression: Consumes more CPU
• Performance regression: Consumes more Memory
• Other

4. Are there any breaking changes?(Y/N) and describe the breaking changes(e.g. more details, motivations or doc link):

• N
• Y

5. Are there test cases for these changes?(Y/N) select and add more details, references or doc links:

• Unit test
• Integration test
• Benchmark (add benchmark stats below)
• Manual test (add detailed scripts or steps below)
• Other

6. Release note

Please refer to Release Notes Language Style Guide to write a quality release note.

None

[coveralls]

Pull Request Test Coverage Report for Build 3013827738

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 2 unchanged lines in 1 file lost coverage.
• Overall coverage decreased (-0.005%) to 60.418%

---

Files with Coverage Reduction	New Missed Lines	%
kclvm/compiler/src/codegen/llvm/context.rs	2	74.15%

Totals
Change from base Build 3013501420:	-0.005%
Covered Lines:	23789
Relevant Lines:	39374

---

💛 - Coveralls

[ldxdl]

LGTM

[chai2010]

LGTM

[He1pa]

lgtm

[zong-zhe]

LGTM

[He1pa]

lgtm