docs: add missing trailing periods in README descriptions

Codebase-wide scan of all 5,485 stdlib package READMEs for blockquote
taglines and h4-description sentences missing a trailing period.
Applies the period to the five clean-drift cases:

- `constants/complex128`: tagline (line 23) and h4 description (line 35).
- `repl/presentation`: `Presentation.prototype.show()` description (the
  only such method whose description omitted the period; all sibling
  prototype-method descriptions in the same file end with a period).
- `stats/base/dists/bernoulli/cdf`: `cdf.factory( p )` description.
- `stats/base/dists/geometric/cdf`: `cdf.factory( p )` description.
- `stats/base/dists/geometric/logcdf`: `logcdf.factory( p )` description.

Other scan hits (`TODO` placeholders, mid-sentence lines that continue
into a following code block or table) are intentional and left untouched.

Author: claude

lib/node_modules/@stdlib/constants/complex128/README.md

@@ -20,7 +20,7 @@ limitations under the License.
 
 # Constants
 
-> 128-bit complex number mathematical constants
+> 128-bit complex number mathematical constants.
 
 <section class="usage">
 
@@ -32,7 +32,7 @@ var constants = require( '@stdlib/constants/complex128' );
 
 #### constants
 
-128-bit complex number mathematical constants
+128-bit complex number mathematical constants.
 
 ```javascript
 var c = constants;

lib/node_modules/@stdlib/repl/presentation/README.md

@@ -912,7 +912,7 @@ function done() {
 
 #### Presentation.prototype.show()
 
-Shows a presentation slide (i.e., writes a rendered slide to the presentation [REPL][@stdlib/repl])
+Shows a presentation slide (i.e., writes a rendered slide to the presentation [REPL][@stdlib/repl]).
 
 <!-- eslint-disable stdlib/no-redeclare -->
 

lib/node_modules/@stdlib/stats/base/dists/bernoulli/cdf/README.md

@@ -87,7 +87,7 @@ y = cdf( 0.9, 1.5 );
 
 #### cdf.factory( p )
 
-Returns a function for evaluating the [cumulative distribution function][cdf] of a [Bernoulli][bernoulli-distribution] distribution with success probability `p`
+Returns a function for evaluating the [cumulative distribution function][cdf] of a [Bernoulli][bernoulli-distribution] distribution with success probability `p`.
 
 ```javascript
 var mycdf = cdf.factory( 0.5 );

lib/node_modules/@stdlib/stats/base/dists/geometric/cdf/README.md

@@ -87,7 +87,7 @@ y = cdf( 2.0, 1.5 );
 
 #### cdf.factory( p )
 
-Returns a function for evaluating the [cumulative distribution function][cdf] of a [geometric][geometric-distribution] distribution with success probability `p`
+Returns a function for evaluating the [cumulative distribution function][cdf] of a [geometric][geometric-distribution] distribution with success probability `p`.
 
 ```javascript
 var mycdf = cdf.factory( 0.5 );

lib/node_modules/@stdlib/stats/base/dists/geometric/logcdf/README.md

@@ -87,7 +87,7 @@ y = logcdf( 2.0, 1.5 );
 
 #### logcdf.factory( p )
 
-Returns a function for evaluating the logarithm of the [cumulative distribution function][cdf] of a [geometric][geometric-distribution] distribution with success probability `p`
+Returns a function for evaluating the logarithm of the [cumulative distribution function][cdf] of a [geometric][geometric-distribution] distribution with success probability `p`.
 
 ```javascript
 var mylogcdf = logcdf.factory( 0.5 );