Add initial structure and two analyzers

[rjmurillo]

Analyzers will be based on guidance from the book Effective C#: 50 Specific Ways to Improve your C#

This change adds the following

• Initial structure for code, test, and benchmarks
• GitHub actions for build, release, PR, and dependabot
• Common extension methods and helper classes for writing analyzer code and tests
• Two analyzers: one for Span and another based on Rule #2 (https://github.com/BillWagner/EffectiveCSharpAnalyzers/issues/2)

[github-advanced-security[bot]]

This pull request sets up GitHub code scanning for this repository. Once the scans have completed and the checks have passed, the analysis results for this pull request branch will appear on this overview. Once you merge this pull request, the 'Security' tab will show more code scanning analysis results (for example, for the default branch). Depending on your configuration and choice of analysis tool, future pull requests will be annotated with code scanning analysis results. For more information about GitHub code scanning, check out the documentation.

[codacy-production[bot]]

Coverage summary from Codacy

See diff coverage on Codacy

Coverage variation	Diff coverage
Report missing for d00a4cc9f61e7d5b392894aad859e46c43a5611c[^1]	:white_check_mark: ∅

Coverage variation details

| | Coverable lines | Covered lines | Coverage | | ------------- | ------------- | ------------- | ------------- | | Common ancestor commit (d00a4cc9f61e7d5b392894aad859e46c43a5611c) | Report Missing | Report Missing | Report Missing | | | Head commit (66e6496c5566b89efd8fad5ef8488cbe074e4bb3) | 0 | 0 | 0.00% | **Coverage variation** is the difference between the coverage for the head and common ancestor commits of the pull request branch: ` - `

Diff coverage details

| | Coverable lines | Covered lines | Diff coverage | | ------------- | ------------- | ------------- | ------------- | | Pull request (#1) | 0 | 0 | **∅ (not applicable)** | **Diff coverage** is the percentage of lines that are covered by tests out of the coverable lines that the pull request added or modified: `/ * 100%`

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_{Codacy stopped sending the deprecated coverage status on June 5th, 2024. Learn more} [^1]: Codacy didn't receive coverage data for the commit, or there was an error processing the received data. Check your integration for errors and validate that your coverage setup is correct.